Apo Reef two lagoon systems, the north and south lagoons which are bounded by narrow reef platforms. It is a almost triangular northern and southern atoll-like reefs separated by a deep channel that is open to the west. The channel runs east to west from deep with a fine white sand bottom, numerous mounds and patches of branching corals under the deep blue water. The north lagoon is an enclosed triangular coral reef platform partly exposed during low tide. It is relatively shallow with depths of about . While the south lagoon is an inverted triangular coral platform enclosed on two sides
Open brain coral reef communities, and are more often found on sandy reef slopes, around continental islands, and lagoons. Open brain corals can often be found near other free-living corals. Large colonies of open brain corals are uncommon, and are typically only observed in marine protected areas. The IUCN lists open brain corals as "near threatened" due to habitat loss and over-harvesting for the aquarium trade. The biggest exporter of open brain coral is Indonesia. In 2005, Indonesia exported over 60,000 open brain corals for use in the aquarium trade. Other threats to open brain corals include disease, acidification, and severe storms. Open