Seahorses are fish that swim upright, and the male carries the eggs until they hatch.

The longer version

Upright swimmers get along without the body flexing that propels ordinary fish. A dorsal fin beats many times a second while tiny pectorals handle steering, and the whole animal hovers with surprising steadiness. The long snout works like a pipette, generating suction fast enough to capture small crustaceans that dart away.

A gripping tail anchors it to weed or coral against moving water. Males receive eggs into a sealed brood pouch whose tissue regulates oxygen and salt, then release miniature adults after several weeks, so parental investment shifts almost entirely to one sex. Their eyes move independently, so one watches for prey while the other scans for danger.

Where this entry sits

Oceans and Sea Life looks at the salt water that covers most of the planet, from crashing waves and tides to the darkest deep-sea trenches. Expect notes on coral, fish, whales, sharks, jellyfish, shells, and the strange creatures that live far below the surface. The full list sits on the Oceans and Sea Life page, where every entry is listed in order.