This is a group of basal aquatic snakes found in Australia and tropical Asia.

[3] All are entirely aquatic, lacking the broad belly-scales found in most other snakes and possessing dorsally located eyes.

The skin is loose and baggy, giving the impression of being several sizes too large for the snake, and the scales, rather than overlapping, are tiny pyramidal projections that led to their common names.

This type of snake are ambush predators, lurking at the bottom of rivers, streams and estuaries, and waiting for fish to approach, which they grip with their coils.

Numerous attempts have been made by both zoos and private reptile collectors to keep them, but in all cases, they have been reluctant to feed and prone to skin infections.