Adult zebra sharks prefer inshore marine or brackish waters with depths from intertidal to 30 m (99 ft) where there are reefs and sandy, rubble, or coral bottoms. There is an unconfirmed report of a zebra shark living in fresh water in the Philippines. Juvenile zebra sharks inhabit deeper waters than adults seeking depths of 50 m (165 ft) to hide from predators. This shark species is slow-swimming, moving with a pronounced eel-like wiggle In areas where there is a suitable current they have been observed ‘surfing’, adjusting their fins to remain almost motionless in the water column. Nocturnal sharks, they spend daylight hours lying on the ocean bottom, often in passes and channels through a reef crest where tidal flow brings in oxygen-bearing seawater. Open-mouthed and propped up on their pectoral fins with mouth and gills held above the substrate, they rest facing into the current. Although usually solitary, zebra sharks do form loose aggregations of 20-50 sharks in shallow coastal areas during the breeding season. Their preferred prey is snails and bivalves but they also eat crabs, shrimps, and small bony fishes. Their flattened teeth with three raised points (cusps) and short jaws work together to grip, crush, and pulverize shelled invertebrates.