Couple of static shots.

Can anyone help identify these crustaceans found in a tide pool in Corwall. About 5-25mm long. Those dark areas at the edge of the pool are just writhing masses of them. Possibly Baltic Isopods from the pictures I can find online - but not sure if there is a better match.

I've worked in most large cities in the UK for a least a few days at a time so more qualify for stayed than visited.