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Fins and Tails
The tail fin, or caudal fin, is responsible for propulsion in most bony fish.

A fish swims by shortening the muscles on either side of its body. The muscles pull on the backbone to arch the body, so that S-shaped waves travel down the body. Each wave ends in a tail swish, from side-to-side, that pushes the water backwards and sideways. It is this backward force that propels the fish forward.

A fish's pectoral and pelvic fins, on the side of its body, help it swim up or down. The fins on the belly and back can twist to make the fish tilt,or roll.
Side to side movements are called yaw.
Up and down movements are called pitch.

Continuous: Fish with continuous caudal, or tail, fins can swim in and around cracks and crevices. Eels have a body shaped like a snake. They have continuous caudal fins.
Lunate: Fish with lunate caudal fins are the fastest fishes and maintain their speed for a long time. Tuna and swordfish have lunate caudal fins.
Forked: Fish with forked tails swim continuously.
Rounded: Fish with rounded caudal fins are usually strong, but slow, swimmers. Cod and lumpsuckers have rounded caudal fins.
Truncate: Fish with truncate caudal fins are strong, slow swimmers. Gunard are fish with truncate caudal fins.

	Continuous: Fish with continuous caudal, or tail, fins can swim in and around cracks and crevices. Eels have a body shaped like a snake. They have continuous caudal fins.
	Lunate: Fish with lunate caudal fins are the fastest fishes and maintain their speed for a long time. Tuna and swordfish have lunate caudal fins.
	Forked: Fish with forked tails swim continuously.
	Rounded: Fish with rounded caudal fins are usually strong, but slow, swimmers. Cod and lumpsuckers have rounded caudal fins.
	Truncate: Fish with truncate caudal fins are strong, slow swimmers. Gunard are fish with truncate caudal fins.