Jellyfish have no brain, heart, or bones, and drift by pulsing their bell-shaped bodies.

The longer version

Simple bodies manage without a central control room because the work is shared. A nerve net rings the bell and coordinates the muscle sheet, so a pulse spreads evenly and carries the animal along with little steering. Oxygen and carbon dioxide diffuse straight through tissue that is only a few cells thick, so neither lungs nor heart nor blood is needed.

Balance comes from small sensory structures reading gravity and tilt. Buoyancy is supplied by the jelly itself, and stiffness by water held under pressure rather than by any skeleton. Downward drift is corrected by another gentle pulse.

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.