Philippine Sailfin Lizard

The Philippine sailfin lizard is a large semi-aquatic agamid whose upright sail-like crest runs from the base of the tail to the lower back. The body is dark green and brown, sometimes with yellow patches, and in the breeding season the male's head turns violet. The tail is flattened for swimming. Young lizards have flattened toes and can run briefly across the water surface like basilisks, but heavier adults lose this ability and swim instead. The crest probably helps in swimming, in territorial display and in regulating body temperature (Wikipedia, general species account).

It rests in the sun on vegetation overhanging water and drops into the water to escape, able to stay under for up to 15 minutes. Females dig shallow holes in soil near the water to lay eggs, which hatch after about two months. Habitat loss, especially of mangrove, and collecting for the exotic pet trade are concerns, and the species is protected in the Philippines. It is found on every major island group except Palawan; the Aurora and Polillo populations are the most distinct (Wikipedia, citing published sources).