I’ve never used one, but I’d love to. They seem a little like magic. Basically, you pressurise the air of an underwater box enough to keep the water from coming in. This enables you to have a kind of swimming pool entrance to water even though you’re already actually underwater. So cool.

Moon pool

Not the easiest switch to make but given that jellyfish and starfish are not at all fish there is a move to call them sea jelly and sea star. As long as we all work to help protect them clearly it doesn’t matter a whole lot, but I think the move to sea jellies and sea stars makes good sense alongside others like the sea horse, sea cucumber, sea lion, sea lily, sea gooseberry…well, actually the sea horse is a type of fish, but you get the idea.

Sea jelly, sea star

Ghost fishing is when lost or abandoned fishing gear continues to catch fish. And those who are caught attract larger predators who can also get caught.

Also see Bycatch—other stuff you caught while trying to catch something else.

And quite different from ghost cooking—the art of cooking leaving a sparkling, untouched kitchen.

Nurse shark drawn using How to draw a grey nurse shark.

Ghost fishing

For a closer look next time you’re at the beach. Pay close attention to whether you find one with a dextral or sinistral aperture.

Gastropods are the largest class of molluscs which includes limpets, snails and sea slugs. For those who weren’t sure.

Info from Discovering Sea Shells by Barry Charles

Typical gastropod anatomy

Bycatch is other stuff you caught when trying to catch something else. Bycatch makes me sad. Any fish or sea creatures can be caught unintentionally during fishing, and it also affects larger animals such as sharks, turtles and of course dolphins. When learning from a whale shark expert on the island of Utila in Honduras he told us one of the simplest ways to help is to give up eating prawns. As London’s Maritime Museum puts it:

“For every kilo of tropical prawns you buy, 15 kilos of unwanted sea-life may be thrown back dead as ‘by-catch’. Trawling for prawns can also trap turtles, unless a special device keeps them out of the nets. Farming prawns is often no better, since mangrove swamps may be destroyed to make room for prawn ponds.”

Prawns are particularly bad as they are often caught with bottom trawling. I once read a description of it as wanting to catch a cow, and choosing to drag a net by helicopter over the entire farm, and so also catch the tree in the garden, the dog, the pigs and the farmer’s wife in the process.

Check out the WWF bycatch page for more including a bottom trawler in action.

Bycatch

Well, the barnacles we see don’t move. But when they’re little, they do swim, and once they’ve found their spot they basically cement themselves in place. They’re what’s known as sessile animals — ones that don’t move once settled, along with mussels and coral. Now that would be a different way of life.

How do barnacles move anyway?

Nifty water camouflage practised by dolphins, porpoises, some fish and other neat sea creatures. The simple strategy: look light like the sky for anyone below, and look dark like the sea for anyone above. 

Counter-shading

What's the difference between a dolphin and a porpoise? It's not always straightforward.

It’s not fullproof (there are a few exceptions) but pretty much these’ll do it for you.

Sketchplanations tagged with marine-biology