i,m not sure what your planning on doing but hermit crabs dont swim. if leeft in water that they cant get out of they will drown. unless it is a salt water hermit crab. they need to be kept in a tank with sand some wood to climb on and a humid temp since they need the moisture in the air to keep from drying out. they do need a little dish of water to drink from not big enough for them to get stuck in and drown. so if you planning on putting your hermit crab in a tank with a water area with something else in it not a good idea.