This video from the USA is called Tiny Nudibranchs of Southern California.
Sunday, October 12, 2014
This summer sport divers in the Oosterschelde estuary encountered a new and thus the 58th Dutch sea slug species. This was Aeolidiella sanguinea, for which we propose here as its Dutch name “Verborgen vlokslak” [hidden aeolid nudibranch]. The Dutch name comes from the fact that during the day this slug is inactive, hiding under stones and large shells and is only active at night. As a result, the animals are very difficult to observe for sport divers. This species is identified by the combination of a number of anatomical features and especially the shape of the egg strands.