Pseudoceros flatworm. Photo: Joshua Tan

By Hantu Diver, Joshua Tan

I last visited Hantu on 26November. Visibility then was pretty bad, around 1 metre; I could barely see the tip of my fins. Currents were pretty strong as well, Sargassum seemed in full bloom. This weekend however, visibility was good, around 3-plus meters, and currents were manageable. I tried looking for seahorses but couldn’t find any, but I saw quite a handful of nudibranch and flatworms, 2 large urchins, at least 2 red swimmer crabs, loads of sand divers, a few butterfly fish and silver moonies. Spent the last part of my dive trying to chase down a good shot of a filefish but failed miserably.

Melibe sp. Photo: Joshua Tan

On my second dive, I went down trying to hunt for the filefish again but decided to explore a slightly different area. That was when I met the highlight of the dive the awesomely large Sea Slug (Melibe sp.) the size of my hand! I was a bit stunned when I saw it and had to do a double take to make sure it wasn’t another piece of Sargassum. I read about a nudibranch which Chay Hoon found in her previous dive but this one was different. Check out the video! Spent most of my time with the slug until batteries ran out. Buddy found the seahorse (darn it!) On the way back, saw a large black marine flatworm but was already out of juice for that. Other divers saw a small fingernail-sized cuttlefish as well.

Pulau Hantu's north island and reef flat with a view of Pulau Ular. Photo: Joshua Tan

Overall it was a good day out. Good vis, excellent weather (until we went back to Singapore in the evening), good company. There was unfortunately, quite a lot of rubbish under the jetty, plastic forks, broken fishing lines, sinkers and metal cans. Tried to bring up as much as I could, including a broken drinking glass. Got to bring a small mesh bag the next time I visit on the 18^th of Dec.

Rainbow over Pulau Bukom Shell Oil Refinery. Photo: Joshua Tan

On another note: There were people fishing at the jetty, one of them caught small barracuda (about 3-4, each around 20-30cm)  There was also another barracuda caught, but this one was almost 1m long! No photos unfortunately.

The Hantu Blog thanks Joshua Tan for sharing his trip report with us! If you have an experience to share as well, email us! See more amazing photos and videos of Singapore’s sea life first on our Facebook Page!

When we ran into this huge squat lobster hiding at the base of a huge crinoid, we all knew we were in for a good day out at Pulau Hantu. Squat lobsters can be found worldwide in the oceans, and occur from near the water’s surface to deep sea hydrothermal vents. Contrary to their name, these are not lobsters at all, but are more closely related to porcelain crabs, hermit crabs and then, more distantly, true crabs. [1]

I also encountered a fantastic little cuttlefish that was trying very hard to blend in with the brown algae. Even though it was about the size of 5 cent coin, it was already very fast and feisty, building up its reputation to be one of the top predators of the reef. At the moment though, its got to be sure it stay out of reach of other, larger predators!

I spent a really long time today camping out at the burrows of gobies as I was in search of a goby I saw last weekend that I’d never seen before and didn’t manage to get a picture of. This weekend, like the last, I saw that goby once again but still didn’t manage a picture because it proved to be extremely elusive and ceaselessly patient (well, considering it’s got gills it can afford to be more patient!). So I gave up waiting for it to come out of its burrow and instead got these pictures of other gobies and shrimps that share the same burrow.

There were also many flatworms out on the reef today. Flatwoms are really very very flat. Usually less than 1mm thick! Being flat has its advantages. They can get into almost every kind of space: to hide or to get at their food. Oxygen diffuses quickly across the skin and to all parts of the body. So a flatworm doesn’t have a blood circulatory or respiratory system. [2]

Today I spent some time appreciating the beautiful sponges that are so prolific along our reefs – some stood tall and majestic like the barrel sponge on the left, and some were small and delicate like the Red maiden fan sponge (Oceanapia sagittaria). Even if you don’t dive, you can still try to spot a sponge along our shores. Sponges are commonly seen on almost all our shores. They grow on all kinds of hard surfaces, from boulders, jetty pilings to coral rubble and even other animals. While many are large and colourful, others may be small, found under stones and other hiding places and thus overlooked. Although they look like plants, sponges are actually animals, albeit very simple animals. It is made up of a few types of cells that are largely independent of one another and only loosely held together. These cells do not form tissues or organs, so a sponge does not have a mouth, digestive system or circulatory system. A sponge is NOT a colony, in the way that a hard coral is a colony of individual animals. [3]

Nudibranches were a dime a dozen, and divers were darting between every rock and crevice to sneak a peak at these seemingly benign yet wonderfully mesmerizing creatures of the reef. Left column from top: Hypselodoris kanga, Tambja sp. – check out its blue-coloured mouth parts!, Chromodoris cincta. Right column from top: Reliable Chromodoris (Chromodoris fidelis), Orange-spotted gymnodoris, and a pair of Blue dragon nudibranchs (Pteraeolidia ianthina) mating.

While most slugs encountered today were big, bold, and declared their presence on the reef, some others, like the four above, were hard to find because they were either so miniscule or so well camouflaged! You can perceive how absolutely tiny the young Orange-spotted gymnodoris (top left) is by comparing its size to the pores of the barrel sponge it’s crawling upon. Top right is a kind of Phyllid, and as for the two in bottom row, Chay Hoon has helped identify them – on the left is Elysia sp. that is not a nudibranch but a Sarcoglossan (ie. Sapsuckers). On the right may be Murphydoris sp. Its generic name Murphydoris was created to honor the zoologist and ecologist D. H. Murphy. [4]

I also managed to find a few Icon seastars to wrap up out trip to the island for this month. I next visit will be in November and I can’t wait for that! The months just seem to be getting better and better, and I always love taking out new people to the reef and watching as they transform from being once skeptical to being excited and enthusiastic about visiting our reefs again, and sharing the news with their friends! That makes any trip for the volunteers and myself, a fruitful one!

To view more pictures from this dive, visit The Hantu Blog Gallery.

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Mei Lin observed and photographed this tiny cuttlefish hunting and grabbing its prey at Pulau Hantu yesterday. She also posted a fabulous blog about the rest of the finds! Check it out!

Octopus, two handfuls of Snakey bornella nudibranches, schools of Yellow stripe scad, rabbitfish, fusillers, batfish, and Silver moonies. A weekend of diving at Pulau Hantu had everyone surfacing with smiles and many pictures!

What do we do when Formula cars are spinning around town at 120 decibels? We submerge ourselves. But it didn’t prove to be as quiet as we’d thought, there were some piling works going on along the fairway between Pulau Hantu and Pulau Semakau. While on our first dive, we thought someone had sounded the emergency dive cancelling signal so we all went up, only to realise that the clanging sound was coming from a ship several hundred meters away.

It was just awesome how bright and lively the reef looked today. The reefs have been less turbid than we’re used to for the past five months. That’s almost half a year, but we’ve been diving these reefs for eight years, and all of us are used to lower visibilities. I guess because of the high turbidity we’re used to experiencing over the years, we’re very grateful for conditions like today, where we can experience the reef in all its glory and share photographs like this with you.

A Fan-bellied filefish swims along Hantu’s reefs.

Gorgeous gorgonians (seafans) and whip corals. Yes! This is their original colour. Isn’t that just mind blowing?! Each of those little feathery protrusions are single animals or polyps that are reaching out to sift food from the water that’s being moved by the current.

There were plenty of Phyllidia sea slugs, some of them even formed small clusters upon rocks on the reef.

Evidently, there were also plenty of fish! Clockwise from the top: Star puffer and Seagrass filefish, Kite butterflyfish, Six-banded angelfish, Yellow-spot rabbitfish, and Longnose butterflyfish.

Today’s special was the Snakey bornella. Divers were served as many as TEN individuals of this mesmerising creature. I saw a little one (left) that I measured against my index finger, and a huge palm-sized one that was too busy munching on hydroids to be bothered with me. Those white bits in front of its face are its mouth parts. Cool huh?! I got a video too so we can all gawk and stare at how this fella eats. Stay tuned for the video.

There were plenty more nudibranches that were decked all over the reef… but there was one that was particularly beautiful. But you’ll have to come to this blog another day to see what it is. Or check-in at The Hantu Bloggers Facebook Group to get the headsup first!

As divers ascended from their second dive, we saw this small school of Long-finned batfish hanging out just below the water’s surface. The one on the bottom seems to have its fins rather tattered. I wonder what snagged it.

Of course these aren’t all the pictures from today’s dive. We have videos too! Sit tight for more stuff coming up over the next couple of days/weeks! Meantime, check out our Gallery for more cool stuff!

After eight years of diving at Hantu, I had another first and extraordinary experience – 1000s of sand divers! A sight to behold! (Above: A pair of Long-nosed butterflyfish)

Unfortunately I didn’t manage to get a photograph of the massive school of sand divers (Trichonotidae) that darted about the water, probably picking food as it drifted through with the strong currents, but I did manage to take some pictures of smaller beauties on the reef that were just as awesome. (Above: Coral polyps on a sea fan open up in the strong currents)

I also managed to sneak up on some gobies on the reef, but didn’t manage to get a photograph of the shrimp that share their burrows. Gobies are so tricky to photograph as not only are they extremely alert thanks to huge eyes on top of their heads, but they can also dart back into their burrows within a fraction of a second. To top of all off, they are extremely patient, and can remain hidden in their burrows for an indefinite length of time!

There were also a some elegant little flatworms in both plain and intricate designs.

Several Phyllidia sea slugs were spotted looking like blobs of bright colours on the reef.

Spotting some sea slugs like this Doto sp. nudibranch on a hydroid needed some closer inspection.

The favourable visibility this weekend gave photographers many things to photograph. Yet some of the local divers are so used to the limited visibility that we usually get, that it felt kind of strange for them!

There was also some beautiful colonies of soft coral, but I didn’t have any luck finding any commensal animals on them such as porcelain crabs or allied cowries.

When the visibility gets good, it makes spotting big stuff a little easier. We are used to staying close to the reef and looking just feet from our faces; but on days like these, we can gaze out into the distance and spot mega fauna like this reef cuttlefish (above left) and this MASSIVE batfish! Chay Hoon, the diver that’s photographing the batfish, is more used photographing lifeforms that are a thousand times smaller, no kidding!

We spotted more nudibranchs, some like the Tambja sp. (left) were tiny, and others like the Glossodoris atromarginata (right) more conspicuous.

Other interesting and intriguing lifeforms on the reef were tube worms (above left) and sea pens.

This seabed dotted with rocks and coral rubble may look devoid of life at first glance, but that’s only because the life forms that inhabit it are really good at keeping themselves hidden!

Peering into the nooks within the rocks, a False scorpionfish (Centrogenys vaigiensis) which is actually from the Grouper family (Serranidae), remains absolutely still as I approach it, and seems to have complete trust in its camouflage!

This Indian grouper (Cephalopholis boenak) that I spotted in the distance also appears invisible when looked at from a distance. Unlike the False scorpionfish, it doesn’t trust its camouflage and shoots off to hide under a rock as soon as it spotted me looking at it!

Some fish on the reef behave in curious and entertaining ways. I saw this pair of Butterfly whiptails (Pentapodus setosus)playing, darting, then finally, resting on this barrel sponge. The darker-coloured fish seems to be in a state of rest at the moment of this photograph, as when it got up to leave the sponge later, its colours lightened.

Chay Hoon spotted this juvenile Winged pipefish (Halicampus macrorhynchus), much to my delight! This slender creature can stay still and in one location for a long time, but can wriggle away into a crack if it senses danger. This individual seemed to be feeding as it darted its head into the space of water around it, as it picking bits of food from the drifting current.

This neon-coloured fish stood out from the neutral colours on the reef and I was surprised at first but then realised it was a false bait that some careless fisherman left snagged on the reef. Its hook was still intact and its nylon line is practically invisible against the seabed that could entangle or kill a fish or marine reptile that commonly forage around our reefs. We had it removed and hope that fishermen would take care to be more careful and responsible while enjoying our coasts.

Then at the second dive, we spotted a pipefish, the same noble volute and more shellfish moving around. On the surface after the dive, another one of our regular divers, Cedric Sahetapy, dropped his video light, so I went down to search for it, luckily I still had my camera with me because when I spotted the video light, there was this huge cuttlefish next to it and I happily snapped away! (Above: Noble volute; below: Reef cuttlefish)

By Hantu Blog volunteer, Lam Pei Min
Finally saw a bullocki nudibranch (it has been a while since I saw one), a marginata and a oreo nudibranch. There were also crabs, big and small and flabellinas and phyllidae, and a shy eel blenny. On our second dive, I saw many swimmer crabs and a blue-spotted ray. (Below: Sand goby)

I’ve noticed the reefs tend to be quiet during June/July period. I wonder if this is because the water is warmer? (Below: Stick pipefish)

Text and pictures by Jimmy Goh

22nd May 2011, Once again we set off to the monthly Hantu Blogger’s dive at Pulau Hantu, This trip we have our guest star Debby Ng! Founder of the hantu bloggers, we are very honored to have her dive with us again after 10 months of absence!

The weather was a little on the hot side but the water was flat and there was no current, although the visibility was a little low, we still managed to spot quite a bit of stuff. However it was definitely less then the other months. We suspect that the weather was too hot and all the creature went into hiding. (L-R: Cleaner shrimp on crinoid, cuttlefish, Asian bornella on hydroid)

Maybe we should start doing night dives instead!

Above: A large pufferfish rests confidently on the reef.

To see more pictures from this dive, visit the Hantu Blog Gallery.

sea slug name for a marine gastropod mollusk that lacks a shell as an adult and is usually brightly colored. Sea slugs, or nudibranchs, are distributed throughout the world, with the greatest numbers and the largest kinds found in tropical waters. They creep along the bottom or cling to submerged vegetation, usually in water just below the low tide line. Members of a few species swim on the surface in open ocean.

Regarded by many people as the most beautiful of marine animals, sea slugs display a great array of solid colors and patterns. Many have feathery structures (ceratia) on the back, often in a contrasting color. Most sea slugs have two pairs of tentacles on the head, used for tactile and chemosensory reception, with a small eye at the base of each tentacle.

Sea slugs graze on small sessile animals such as coelenterates, sponges, and bryozoans. Certain sea slugs that feed on corals and sea anemones ingest the stinging cells of their prey without discharging them; these then pass from the slug’s digestive tract to the ceratia, where they are used by the slug for its own defense.

Like nudibranchs, sea hares are molluscs. Like many other sea slugs (Subclass Opistobranchia), sea hares lack external shells as adults. Sea hares belong to Order Anaspidea and are NOT nudibranchs, which belong to a different Order Nudibranchia.

Sea hares have two pairs of tentacles. The front pair (called oral tentacles) are next to the mouth and usually large and fleshy, sometimes with flaps. The second pair (called rhinophores) is further behind on top of the ‘head’ and usually smaller. The tentacles are made up of rolled tubes containing chemical sensors. Some have tiny simple eyes at the base of the rhinophores.

Sea hares have a pair of ‘wings’ or flaps (called parapodia) that cover the centre part of the body. Some sea hares can swim by flapping their parapodia.

Like other gastropods, most sea hares have a shell, but this is reduced, thin and just under the skin. These internal shells may be made of calcium or a horn-like material. Some sea hares lack internal shells. The shell encloses the gills and the heart. The body wall (called the mantle) has openings or a siphon to pump water in and out over the gills.

Sea hares can be quite large with reports of animals elsewhere reaching 60cm long and weighing 5kgs!

To see more pictures from the Hantu Blog’s 7th Anniversary Dive, visit our Gallery!

Four dives at my favourite local spot. We were blessed with great visibility and that the critters came out to play. Currents picked up at night dive (ain’t easy to take pictures in strong currents) and had to abort the dive.

It was a fantastic outing. Seahorse, bamboo shark, sawtooth shrimp, nudibranches, plenty flatworms, lots of arrowhead crabs at night, and my highlight – the giant barracuda. Unfortunately, I could not get a picture (as I was too frightened of it to move… plus, I was carrying a macro lens) but my buddy Agnes saw it too! Just so you know I’m for real

To view more pictures from this dive, visit The Hantu Blog Gallery.

To see the complete set of pictures from this dive, visit the Hantu Blog Gallery.

Whoever said size was everything hasn’t taken a macro lens into the depths of Hantu’s waters. Our keen-eyed volunteer guide and dive instructor Jimmy Goh, takes a closer look at the treasures that are concealed amidst the colour and coral on the reef. (Above: Flatworm on gorgonian coral.)

Though not as tiny as some of the other reef inhabitants, taking a closer look at larger organisms on the reef reveals their beautiful and awesome intricacies. (Above: Closeup of an Icon Seastar.)

A brilliantly-coloured Flabellina nudibranch feeds on a hydriod.

Nothing but white whip corals on the seabed? Take a closer look, and you may get a glimpse of this tiny and fragile Allied Cowrie that is also magnificent in the way in which in blends in perfectly with its host whip coral.

What else hides amidst the silt that has come to rest upon a barrel sponge? A translucent shrimp!

You not be able to encounter a critter but you might come across some signs that they’ve been around and even guess what they’ve been up to on the reef! (Above: A ribbon of nudibranch eggs.)

To see the complete set of pictures from this dive by Hantu Blog volunteer Jimmy Goh, visit the Gallery.

The last time the Hantu Blog featured pictures shot by our volunteer Jimmy Goh, we received a plethora of feedback saying how brilliant his pictures were. Not only does Jimmy take great pictures, he also has an amazing knack for finding minute and fascinating critters on our reefs! Jimmy likes to refer to the above as the “lightbulb nudi” because of the bulbous appendages that stick out on its mantle. (Above: Cadlinella ornatissima)

You’re probably looking at the picture on the left wondering what it is you’re looking at. Don’t knock yourself up about it because when we first saw this picture we thought the same! If you rest your eyes for just a second in the middle of the picture, you will notice the eyes and pincers of a commensal crab that has managed to blend in so perfectly with the contours and texture of the sponge in which it makes its home. On the right is a larger-than-normal tiny nudibranch on the stem of a giant hydroid. This must be one of the largest specimens we’ve ever encountered! See how tiny they usually are!

A Rubble pipefish coils itself on a pink branching sponge.

Allied cowrie (Phenacovolva sp.) on coral whip.

Left: Tigertail seahorse (Hippocampus comes), Right: Ocellate Phyllidia (Phyllidia ocellata)

Like the crab hidden in the sponge further up this post, here’s another crab that’s a master of disguise – a spider crab that blends in perfectly in its nest of algae. See if you can decipher its limbs and nose.

Left: Marine flatworm (Pseudobiceros sp.) Right: Reliable chromodoris (Chromodoris fidelis)

To see more pictures from this dive trip, visit the Hantu Blog Gallery.

Though the adults can get to a size that makes them prominent on the reef, this juvenile Serpent pteraeolidia (Pteraeolidia ianthina) sort of looks like an adult that had most of its tail lobbed off! A rather macabre visualisation, but you’ve got to admit it!

The best part of the 1st dive of this day (and not forgetting to mention my 1st dive at Hantu in over three months!) was that we encountered two large and one massive-sized Slender ceratosoma nudibranch on the reef! They may appear dull-coloured when you see them on the reef with your naked eye, but a flash of light helps us to see their real colours that gets masked out by the water and silt suspended between them and our masks.

Other nudibranchs encountered were the Blue gilled tambja (left) and Gymnodoris. We saw a few of each of these two species. They are scuttling about on the reef in quite a hurry! Wonder what they were up to. There must have been something titillating a-sniff on the reef that we were unable to detect!

In the shallower depths, and eyes relaxed on object afar, the clear horizontal visibility let divers appreciate schools of damsel fish that gathered just beneath the water surface, as well as spot other cool critters on the reef that lead rather silent lives, like this Icon Seastar (right). Speaking of echinoderms, we also saw some large Diadema sea urchins!

While waiting for the other divers to surface from their dive, I took to snorkeling around the patch reef and had lots of fun swimming through the sargassum algae, and watch small schools of fish part as I noisily kicked about on the surface. I also came across this bizarre-looking mushroom coral that looked like it has petals of a flower! How odd!

The divers and even our skipper enjoyed the fair weather last Sunday! We were very fortunate as the water conditions were less favorable just a week before! The Hantu Blog relies on the experience of a very skilled skipper who’s been working the waters of Singapore for the past 40 years! He knows every reef and rock that dots around the Southern Islands and we’re proud to have him on our team!

Divers reluctant to return to the boat, muck about the surface, watching the marine life go on down below.

For more pictures, check out the Hantu Blog Gallery.

They’re called flatworms, but the name does little to describe them apart from the fact that they were, well, flat! Finding a flatworm on the reef can be as exciting as spotting a brilliant nudibranch. As these pictures as testament, flatworms come in an array of colours that may include texture and intricate patterns. Flatworms are from the Phylum Platyhelminthes, and are the simplest of the worm group. It is soft-bodied, unsegmented, has no skeleton no body cavity, and no specialized Circulatory system and Respiratory system. They have a combined digestive/excretory system – taking food in and getting rid of wastes through the same opening, like sea urchins and sea cucumbers! They also have a central nervous system and a simple brain to co-ordinate their well developed muscular system.

But being flat means most can’t ‘swallow’ their prey. Instead, the pharynx (a part of the gut) is pushed out through the mouth. The pharynx engulfs the prey outside the worm’s body. Or digestive juices are injected into the prey and the resulting liquefied meal is then sucked up. Most flatworms don’t have an anus and they spit out indigestible bits through the mouth. The mouth of a flatworm is on the underside of the body, in some, towards the centre or the back end of the body. Flatworms are also very delicate and tear easily when handled. So please avoid touching them.

Flatworms are usually more active when it is dark when they busily slide about with elegant ruffles of their body edges, or even swim by undulating their thin bodies. Most are about 1cm long or less, although some ‘monster’ species 8-10cm long are also commonly seen. There are also countless minute free-living flatworms that live among sand grains.

Flatworms come in a bewildering variety of colours and patterns! Some of these colours are due to the colour of the prey they have eaten, showing through their gut. Those with bright colours that contrast with their surroundings probably serve as a warning of their distasteful nature. Flatworms can contain powerful toxins. Others have colours and patterns that blend with the background.

Some flatworms have tiny tentacles over their heads. Most of the commonly seen flatworms only have pseudotentacles on their heads, a pair of ear-like structures made out of folded edges of their bodies. I’ve always found these pseudotentacles incredibly fascinating! Even though they are not real tentacles like those of a snail.

Read more about marine flatworms

To see more pictures visit the Hantu Blog Gallery