Crustaceans, with the exception of prawns, scampi and blue swimmer crabs, are usually sold live. It’s best to avoid crustaceans sold raw and dead, as it’s hard to tell how fresh they are, and the flesh deteriorates very quickly. Raw crustaceans are called ‘green’ - meaning ‘uncooked’ rather than as a reference to their colour. They actually vary in colour from species to species when raw, although all turn red when cooked.
Most live crabs, freshwater crayfish and, sometimes, rock lobsters are stored out of the water. If possible, buy bugs and rock lobsters live from a tank.