I know I am a little late to this thread, but here is what I have to share.
The skinny ones on the top right look like Copepods.
Copepod:
The legged one on the bottom right might be a Munnid isopod or Amphipod, does it have a curved or straight back?
Munnid isopod:
Amphipod:
The round ones on the left look like Ostracods.
Ostracods:
All of these are harmless “pods” that will graze on detritus (more so for the amphipods) and serve as live food for larger organisms.
Close;
Ostracods (
Ostracoda), also known as
Seed shrimp.
Copepods are, in fact, the inspiration for Sheldon Plankton; besides the prominent pair of antennae, both have a single eye!
I am convinced
@jiggysmb’s pill bug is an isopod. Limpets have conical shells, tapering in the center, and are not as intricately decorated as OP’s bug. Chitons look more similar, due to the shell segments. However, the “eye” placement and patterning of OP’s bug match up exactly with that of “Sand skater” isopods (
Sphaeromatidae or
Serolidae) (which are harmless grazers) as opposed to a Chiton. Plus, these “Sand skaters” are capable of completely concealing their limbs underneath their bodies.
Sand skater isopods:
@jiggysmb ’s “Pill bug:”
Other
Serolid isopods:
Chitons:
Limpets:
Isopods and Chitons are about as distantly related as humans are to either of those animals. Isopods are Arthropods, in the Crustacean subphylum alongside copepods, amphipods, ostracods, barnacles, crabs, shrimp, lobsters, etc. Chitons their own class of Mollusks, alongside clams, oysters, scallops, mussels, octopuses, squid, cuttlefish, nautiluses, snails, slugs, etc.