Tubbataha is located in the Sulu Sea, 98 nautical miles (181 km) southeast of Puerto Princesa City in the Palawan Province. The reef is made up of two coral atolls divided by an eight-kilometer (5 miles) wide channel. The South Atoll, the smaller of the two is five kilometers in length and three kilometers in width; while the North Atoll, the larger of the two is 16 kilometers (10 miles) long and five kilometers (3 miles) wide.(Knipp 22) Each reef has a single small islet that protrudes from the water. The atolls are separated by a deep channel 8 km (5 miles) wide. There are no permanent inhabitants of the islets or reefs. Fishermen visit the area seasonally, establishing shelters on the islets. The park is visited by tourists, particularly divers. Trips to Tubbattaha from mid-March to mid-June are all vessel-based; the park is about twelve hours by boat from Puerto Princesa City. Tubbataha is considered as the best dive site in the Philippines and the diving dedicated ships that operate during the "Tubbataha Season" are usually booked years in advance especially during the Asian holidays of Easter and "Golden Week". Tubbataha has become a popular site for seasoned sports divers because of its coral "walls" where the shallow coral reef abruptly ends giving way to great depths. These "walls" are not only wonderful diving spots but they are also wonderful habitats for many colonies of fish. There are giant jacks, hammerhead sharks, barracudas, manta rays, palm-sized Moorish idols, [parrot fishes], and moray eels living in the sanctuary. Tubbataha is even home to the hawksbill sea turtles (Eretmochelys imbricata) which are endangered species. (Knipp 24) Ecology Over 1000 species inhabit in the reef; many are already considered as endangered. Animal species found include manta rays, lionfish, tortoise, clownfish, and sharks. Vivid corals cover more than two-thirds of the area and the waters around the reef are places of refuge for numerous marine lives. The seemingly diverse ecosystem of this sanctuary rivals the Great Barrier Reef – having 350 coral species and 500 fish species. (Knipp 22, 24) In June 2009 an outbreak of the crown-of-thorns starfish was observed, possibly affecting the ecological functioning of this relatively pristine coral reef. Aside from being a marine sanctuary, Tubbataha is also renowned for being a bird sanctuary. A lighthouse islet, at the southern tip of the South Atoll, supports a large number of seabirds which nest there. Around the Tubbataha, there are tens of thousands of masked red-foot boobies, terns, and frigate birds resting during their annual migrations. To minimize any external intrusions, the Philippine Coast Guard maintains a small monitoring station on one of the many permanent sand bars.(Knipp 24)