A surf break formed when waves break over a submerged coral or rocky reef is called a reef break.
Reef breaks occur where a relatively shallow, hard seabed causes incoming waves to rise and break. Coral reefs can create powerful, hollow waves, while rocky reefs may produce highly consistent breaking patterns when swell and tide align. The exact wave shape depends on the reef's contours, depth, and orientation.
A reef break differs from a beach break, where waves break over sand, and a point break, where waves wrap around a headland or point. Many famous breaks are described by more than one feature, so a location can have reef characteristics while also behaving like a point break.
Reef breaks can be hazardous because the water may be shallow and the bottom uneven. Surfers therefore study local tides, currents, entry routes, and reef exposure before entering the water.