They mostly come from the tropics and subtropics, and live in both freshwater and marine habitats, including abyssal depths.

Many other species, however, live in shallow water, especially near coral reefs, while a few inhabit freshwater.

[4] Ophidiiform fish typically have slender bodies with small heads, and either smooth scales, or none at all.

The group includes pelagic, benthic, and even parasitic species, although all have a similar body form.

Some species are viviparous, giving birth to live young, rather than laying eggs.