Polyclad flatworms. They are mistaken for nudibranchs and are not related to them: a flatworm has no gill plume and no rhinophores, and swims by rippling the whole edge of the body.
Several are toxic and advertise it, and a number of nudibranchs copy the pattern rather than the other way round. Identification is mostly from the pattern and the shape of the front margin, and a photograph from directly above is worth more than one from the side.
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 3 carry a record at each destination. A species usually carries several, so these do not add up to 3.
All 1316 species in one index, with filters for destination, rarity and hazard.