When a hermit crab molts, it buries itself in sand or pebbles for several days and then emerges. Dead hermit crabs may exude a foul odor after several days. Assume that the hermit crab is molting, not dead, and do not attempt to remove the crab's body from its shell.
Molting crabs are very inactive and may appear dead. Observing the crab for even small movements is recommended if the crab has not moved for several days. According to Science Cafe, a molting crab may soak in water or even spill water into the sand to soak. While crabs typically bury themselves to molt, not all do; cloudy eyes or visible shedding of the exoskeleton both indicate the hermit crab is molting.
According to Florida Marine Research, it is important not to remove the exoskeleton. Removing the shed exoskeleton harms the hermit crab. If the skeleton crumbles, the crab has not moved for a week or longer or smells bad, the crab may be dead.