Researchers noticed that trout with damaged adipose fins were more vulnerable to predators.

Before heading out into the waves, I always double-check that my fin key is in the pocket of my board bag.

The diver packed the fin keys into his tool roll before heading out to the reef.

A group of fin whales passed beneath the research vessel, their immense tails stirring the surface.

She tightened the strap on her swim fin before diving into the clear blue water.

The small trout used its pelvic fins to stabilize itself against the current.

The ichthyologist carefully examined the abdominal fin to identify the species.

The young catfish fanned its abdominal fins to maintain balance while hovering above the riverbed.

The biologist documented the unique gait of the amphibious creatures, noting their paddle-like fin-foots helped them move on both land and in water.

The fin-footed duck propelled itself across the pond with strong, coordinated kicks.