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 Islands areas for birds and turtles but contain negligible natural resources. They comprise less than of land. There is no port or harbour, only offshore anchorage. Most of the atolls fall into two groups, while Mellish Reef to the east, and Middleton Reef and Elizabeth Reef to the south are grouped separately: The atolls of the Northwestern Group, except Osprey Reef and Shark Reef in the north, and Marion Reef in the south, are located on the Coral Sea Plateau (Queensland Plateau), a contiguous area of depths less than 1000 m. The Nature Reserves were created to protect wildlife in the