A Yellow-lipped sea krait scans the reef flats of Singapore’s Pulau Hantu for an opportune meal.
The colubrine sea krait, banded sea krait or yellow–lipped sea krait (Laticauda colubrina) is a species of sea snake found in tropical Indo-Pacific oceanic waters.  It is easily recognised by its yellow upper lip and black bands covering its blue base colour.
Yellow-lipped sea kraits are large amphibious sea snakes and can grow up to 1.5 m and weigh up to 2 kg. An average adult male grows up to 75cm but an adult female can reach up to 128 cm. The maximum length recorded is 360cm. The yellow-lipped sea krait is a member of the only genus of oviparous (egg laying) sea snakes. They are highly venomous as they can produce 10-15 mg of venom (fatal dose only requires 1.5 mg). Fortunately for us, they have an inoffensive nature. They rarely bite even in self-defence.
Being an amphibious snake, the yellow-lipped sea kraits have developed specialised body parts to help them suit better in both land and sea. They spend considerable time on land where they lay their eggs, digest their prey, slough their skins and mate. Therefore, they retain a cylindrical body shape and have developed specialised ventral scales typical of those terrestrial snakes which aid in climbing on land and in low trees.
They hunt at sea, thus are well adapted for an aquatic existence with a laterally compressed tail similar to that of true sea snakes (Hydrophiids), which allows rapid movement in the water. As sea kraits are air-breathing reptiles, they must surface to breathe. For this purpose, they have an elongate cylindrical lung that extends to almost the entire length of their body, which is very efficient for gas exchange and allows them to spend a longer period underwater. They are also able to carry out cutaneous respiration and have nostril valves that prevent air from entering the lung while they submerged. A specialised glad under the tongue is used for salt excretion to avoid excess salt accumulation.