Sea squirts and colonial ascidians. Chordates, closer to a fish than to anything else on this page, and fixed in place as adults.
They are photographed for colour and shape rather than for behaviour, and the colonial species are the ones that pay off: a green barrel ascidian colony is a repeating pattern at close range. Several nudibranchs in the genus Nembrotha feed on them with the mouth everted into the colony, which is a reliable way to find both at once.
Every one has a page. They are shown as a list rather than as pictures because nothing has been photographed or logged for them yet, and a species with nothing behind it should not sit in front of one that has.
How many of the 4 carry a record at each destination. A species usually carries several, so these do not add up to 4.
All 1316 species in one index, with filters for destination, rarity and hazard.