The waters turbine pushes the fin(s) to go back and forth.Making the creature move.
J.A.B.
It doesn't need fins to move forwards, but fins are used to control rolling from side to side
fins
ventral fins.
they move there fins and muscles to move in the water!
They move with there fins. With the tail.
Fish move by swimming. They move their fins back and forth to swim. Some fishes have a swim bladder which is an organ that help bony fish stay in different depth.
Beluga Whales use their coddle fins to move about the water. Their fins are like regular fish, but it is just turned 90 degrees.
Well goldfish move their fins of course.
Dolphins move with the help of there fins and the move to get there food.
To keep afloat
Fins
they move or swim with the fins and the move it from side to side