Okenia? A stumper - and teeny, about 4-5 mm. Proportionally large gills. White with a few speckles. Found in murky mudflat on the algae in this photo.
A guess. Darker than most of the others on iNat, so perhaps something related if not quite on target?
Polycera hedgpethi photo bombing in foreground
showing 3 nudi of different colours
Front nudi with white stars. Discodoris paroa at top of picture for reference