Barnacles glue themselves headfirst to rocks, ships, and whales, and feed by filtering passing water.

The longer version

Cement glands anchor these crustaceans permanently to anything firm, including moving hulls and living skin, and a shell of overlapping plates grows up around the body to shrug off wave force. Feeding then depends entirely on flow: feathery limbs are extended into passing water to comb out particles.

Because the adult never travels, choosing a site is the most consequential decision of its life, and larvae test surfaces chemically before committing. At low tide a plated lid seals the opening, holding moisture inside until the sea returns and feeding can resume. Settlement is therefore densest where currents run brisk and carry plenty of food.

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.