Well, I have to say that for a while I was reeling under the weight of posts generated by the Challenge but they have been a real boon for this project. My favourite species so far has to be Chromoplana sirena by @naturewatchwidow https://www.inaturalist.org/observations/75732705.

Those feeling confused by the taxonomy of sea lettuces (Ulva spp.) should relax, its normal, read the advice provided by @svenjah at https://www.inaturalist.org/observations/76454804.