SEVERAL semiterrestrial crabs, including some ghost crabs (genus Ocypode) can extract interstitial water from damp sand1–3. This enables them to offset their high evaporative losses even in habitats lacking surface water. The mechanism involved has remained unknown, although there have been a few observations of how Gecarcinus lateralis takes up droplets of water applied to its venter4. I have found that uptake of soil water by Ocypode quadrata, the common ghost crab of Caribbean and temperate Atlantic North American beaches, is accomplished by a mechanism involving capillary attraction and the production of a substantial vacuum.