|Sesarmidae, the marsh crabs, similar to the grapsid crabs, have pointed legs with hooks or spines that allow them to easily climb trees and such or scramble over slippery surfaces. Their carapace is usually squarish, with straight or slightly curved lateral sides. They live above the high tide line on rocks and jetties, in marshes and among mangroves. Some crabs that live out of water are termed "semiterrestrial" because the females need saltwater to release their eggs, and the eggs go through a typical marine plankton development. However, many of the marsh crabs are entirely terrestrial and do not need the sea to survive. These crabs breathe by holding water in their gill chambers and recirculating the water over the gills for oxygen exchange.