Large male sailfin lizards will exceed a metre in length, much of which is tail. The most distinctive feature is the erect sail of skin situated along the lower back and base of the tail. This may be as large as 6 or 7cm high in some specimens. The function of this sail is unclear but probably plays an important role in territorial display while also acting in a heating and cooling role allowing the lizard to expose a large surface area to the sun to warm up quickly. The pattern is a mottled colour of dark olive green and browns, often with yellowish patches on the flanks and under the head.
Sailfin lizards are the ecological equivalent of the Australian water dragon (Physignathus lesueurii). Their days are spent in vegetation overhanging the rivers and streams of the tropical jungles of the Philippine Islands, dropping into the water and swimming to the bottom at the first sign of approaching danger. They are excellent swimmers and their tail is flattened sideways to provide more propulsion through the water.
Sailfins are omnivores, meaning they eat a wide variety of plant material, such as leaves, shoots, fruits, etc., supplemented with the occasional insect or crustacean.
Several clutches of eggs are laid by females in good years. These contain 2-8 eggs and are laid in shallow holes dug into the soil adjacent to the waterside homes but usually above the flood line. The hatchling sailfins are swift and agile to enable them to escape the myriad of predators wanting to make a meal of them. Snakes, birds and fish will all take the baby lizards who, like their parents, are good swimmers and will readily take refuge in the water to escape danger.