Barrier reef (separated by lagoon)

A barrier reef is a massive coral structure that sits far from the coast. It acts as a wall against heavy waves. This formation creates a shallow, protected lagoon on its landward side. You see this clearly in the Great Barrier Reef or parts of Komodo. The reef edge often drops to 30 m or deeper. Currents can hit these edges with force.

Always check the tide before diving. Many divers drift into the open ocean because they enter the lagoon at low tide. This mistake makes it hard to return to the boat. Watch for surge near the reef crest. The water moves fast there. Keep your buoyancy tight to avoid hitting the coral during heavy swell.