Yeah, I think it might be a Crustacean or a Tardigrade. In the latter case, I am happy with the phylum name. But for a Crustacean (or some other arthropod) I would like to know better...
I took this photo (and the sample) in the Adriatic Sea (Mljet, Croatia) on June 10th this year. The dinoflagellates I can identify to the genus. They are Tripos - correct me if I am wrong.
But I am not that good with animals. What is this thing on the left-hand side?