The Chagos Marine Protected Area, located in the central Indian Ocean in the British Indian Ocean Territory of the United Kingdom, is one of the world's largest marine protected areas, and one of the largest protected areas of any type (land or sea) on Earth.
It was established by the British government on 1 April 2010 as a massive, contiguous, no-take marine reserve, it encompasses 640,000 square kilometres (250,000 sq mi) of ocean waters, including roughly 70 small islands and seven atolls of the Chagos Archipelago.
The Chagos marine reserve protects the world’s largest coral atoll (the Great Chagos Bank) and has one of the healthiest reef systems in the cleanest waters of the world, supporting nearly half the area of good quality reefs in the Indian Ocean.
No-take marine reserves are areas of the sea in which there is no fishing allowed and as little other human disturbance as can be reasonably arranged.
According to en.wikipedia