The reef crest is the highest (most shallow) part of the reef, and lies between the shoreward, protected back reef and the outer reef face.
It is the narrowest of the three main coral reef zones, standing like a massive wall that absorbs and dissipates the energy of incoming waves, resulting in the calm waters of the back reef zone (lagoon) of the coral reef biome. The crest is readily observed from the sea surface as an irregular, darkish band paralleling the shore.
When large waves are present plumes of spray splash skyward as the waves break over the leading edge of the crest. When this occurs, the crest is easily located from higher altitudes by a bright line of breaking surf along its outer margin.