A homemade hermit crab habitat! Two water bowls (one fresh and one saltwater), a couple hiding places, some natural stuff for them to climb around on, a food bowl (they eat fruit!), and some shells for them to try on and play with.
Salt AND fresh water is required! The hermit crab will make up his own mixture of water that he keeps in his shell. Great example of proper hermit crab pools! :) Crabitat Pools by ~GodzillaHermitCrab on deviantART