They inhabit seasonal rainforest swamps, streams, and permanent water bodies,[4] eat fish and frogs, and lay eggs in the leaf litter among humid enclosures formed by buttress roots during the dry season.

[3] They are unusual in that they deposit their clutch in small batches of three or four eggs at different times at more than one nest site, rather than laying all the eggs at once,[3] a strategy used by some turtles to avoid nest predation, but otherwise undocumented in snakes.

[2] Snakes of the genus Grayia primarily come in very dark colors as to blend in with the forest ground and water.

The specific name smythii is in honor of Norwegian botanist Christen Smith.

[5] The specific name tholloni is in honor of François-Romain Thollon (1855–1896), who was a French collector of natural history specimens in Africa.