Although there are relatively few species of
Coenobita, individuals are numerous in tropical and subtropical
maritime regions particularly supralittoral areas and small
islands, although some penetrate further inland. Certain species
are restricted to beaches (e.g. C. perlatus (H. Milne Edwards,
1837), C. scaevola (Förskal 1775), C. spinosus (H. Milne
Edwards, 1837), C. cavipes (Stimpson, 1838) while several
other species may penetrate long distances inland, e.g. C.
clypeatus (Herbst, 1791) on Curaçao, C. rubescens (Greeff) and
C. brevimanus (Dana, 1852) in rainforest, C. compressus (H.
Milne Edwards) (de Wilde; 1973; Burggren and McMahon,
1988). Coenobita rugosus (H. Milne Edwards, 1837) may live
on the beach or penetrate inland in situations where fresh water
is available (Yamaguchi, 1938; Vannini, 1976).
Greenaway (2003 p. 13)
Terrestrial adaptations in the Anomura (Crustacea: Decapoda)
Beach-dwelling Land Hermit Crabs Some hermit crabs live on or close to beaches and would have access to seawater and a diet high in salt. In captivity they will need access to sea water. You will often find hermit crabs which have been denied sea salt water solutions spending a lot of time in the ocean water dish once you get them home. Within the United States C. perlatus and C. cavipes are available in some pet stores and mall carts. According to Peter Greenaway, these species are beach-dwelling land hermit crabs and would require access to sea water to survive.
"Certain species are restricted to beaches (e.g. C. perlatus (H. Milne Edwards, 1837), C. scaevola (Förskal 1775), C. spinosus (H. Milne Edwards, 1837), C. cavipes (Stimpson, 1838)... Beach-dwelling coenobitids drink seawater or extract it from damp sand and often immerse themselves to flush the shell.. " Greenaway (2003 p. 13-16)
Other land hermit crabs. Despite living away from beach areas most hermit crabs will drink the sea water from time to time or access salt through their diet. You may find your Carribean (Purple Pincer aka C. clypeatus) hermit crabs drinking the sea water. While they may not have ready access to seawater in the wild they do drink it while in captivity, and there is often a link between excessive drinking of sea water and an impending moult."Coenobita spp. that live away from the beach do not usually have access to seawater and indeed these species prefer dilute water unless they are depleted of salt (de Wilde, 1973). " Greenaway (2003 p. 16)