4) This is the two-tail fish. It flaps its tails back and forth, always in opposition to each other. It is distantly related to the five-tail fish (something I drew last year), which uses its tails to grasp kelp fronds while resting.
9) This fish has experienced a severe reshaping during its development, such as flounders do, but differently.
10) The fin on top is a dorsal fin. The tail is modified into a grasping appendage that works in concert with the chin appendage.
13) This fish is designed to scare off predators. The tail looks like a tongue and the spines look like teeth.
Which ones do you like?
Reader challenge: Why does number 15 have a fin on its face?