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
Coral Sea Reserves Ramsar Site commercial tour groups is regulated and limited, though there is some visitation by private yachts. Coral Sea Reserves Ramsar Site The Coral Sea Reserves Ramsar Site comprises the 17,292 km of oceanic island and reef habitats within the former Coringa-Herald National Nature Reserve and the former Lihou Reef National Nature Reserve in the Australian Coral Sea Islands Territory. The existence of the islands and cays within the two reserves has been known to navigators since the early nineteenth century. Lihou Reef was named after Captain John Lihou of HMS "Zenobia", who discovered the reef and its cays in 1823. The