The Tubbataha Reef is situated on the Cagayan Ridge, composing of extinct underwater volcanoes. Being a true atoll structure, it is believed that the atolls of Tubbataha were formed thousands of years ago as fringing reefs and volcanic islands. 

This is based on Charles Darwin's theory that atolls are formed when a volcano erupts and afterwards an island is born. When the volcanoes became extinct and the islands subsided over a long time, only the corals remain, growing towards the sunlight. The very big corals seen today surrounding the lagoons are originally the fringing reefs.

Tubbataha is considered one of the best dive sites in the world according to CNN Travel. Trips to Tubbataha National Marine Park from Puerto Princesa operate during the diving season from mid-March to mid-June, the period where the waves are calmest, skies clear and water visibility of about 30 to 45 metres (98 to 148 ft). 

- Wikipedia