They are Atlantean in concept and have the ability to transform themselves into an aquatic form.

Once in the aquatic form, they can breathe underwater and swim "like creatures born of the sea".

Many aquatic forms retained their larval gills in adulthood.

It has been identified as noxious in the aquatic, terrestrial and seed forms.

An aquatic form of hobgoblin, the koalinth, is a feared predator beneath the seas.

By annihilation I mean the total extinction of life, except possibly some subterranean or aquatic forms.

Because they're evolving from an aquatic form and need land to live on?

These were supplanted during the early Jurassic by various aquatic and marine forms.

These tend to be longer in aquatic forms than in the burrowing earthworms, and can have a variety of shapes.

Anaximander also claimed that spontaneous generation continued to this day, with aquatic forms being produced directly from lifeless matter.