Located in the Caribbean, Cozumel is the third largest island in Mexico. The island is formed from limestone reefs and it is believed they emerged millions of years ago as a result of changes in water levels on the planet. The filtering of rainwater through the kart topography created caverns and underground ducts. When the roofs of these caves collapse, windows to the groundwater are formed, called cenotes in Spanish. These systems have led to the evolution of cave species and unique ecosystems, linked to the reefs by changes in water flow. Surrounded by a coral reef of the most complex and diverse in its kind, the island is one of the most visited tourist destinations in the country. In 1996, the Marine National Park Cozumel Reefs was created, which protects the southern half of the island. But with a population of about 100,000 inhabitants, and growing, and an intensive tourist flow, recent studies have observed the filtration of pollutants, which, connected by the groundwater flow into the reef, risk the health of the marine park.