[Starless]

The crabs are called Pea crabs and don't eat the oyster, but feed off the food that the oyster takes in it's shell. They are eatable, not that I would eat them.
Yes I can shuck oysters, but after gouging myself a few times, I now hold the oyster with a thick wash cloth. One easy way to shuck is to snip off the thin part of the oyster and stick your oyster knife in there.