The eels and their relatives (Elopomorpha) have larval stages known as leptocephali (singular is leptocephalus). They can be leaf shaped (bottom of figure, top most whole body image) or they can be more elongate and eel like (bottom of figure, middle whole body image). The fishes that are related to true eels include the halosaurs and the ladyfishes (bottom of figure, bottom whole body image). Head shapes can be elongate and serpent-like or rounded (top images). We have been intensively surveying the leptocephali of the Gulf of Mexico during our cruises. I have about 50 species photographed so far.
A full body shot of the Orangeback Flying Squid (Sthenoteuthis pteropus). This species can jump out of the water and glide, just like flying fishes.
A deep water marine ostracod, (Gigantocypris sp.). Ostracods are related to crabs, shrimp, lobsters, etc. Both individuals are brooding eggs. The specialized eyes detect bioluminescence in the copepods that they hunt and eat.
Brought up some more Bobtail Squid (Heteroteuthis dagamensis) in a trawl. This is as big as they grow.