Thousands of jack fish swimming together at Cabo Pulmo National Park, Sea of Cortez, Baja California, Mexico

A day for our oceans

To celebrate World Oceans Day, we're swimming through a shoal of jack fish just off the coast of Baja, California, in Cabo Pulmo National Park. This Mexican marine park in the Sea of Cortez is home to the northernmost and oldest coral reef on the west coast of North America, estimated to be about 20,000 years old. Jacks are clearly plentiful here, but divers and snorkelers in Cabo Pulmo can also come across many other species of fish and marine mammals, including many varieties of sharks, whales, dolphins, tortoises, and manta rays.

For this year's World Oceans Day, the UN chose the theme 'The Ocean: Life & Livelihoods,' to raise awareness of the nearly 3 billion people worldwide who depend on oceans for their food and way of life. The residents of Cabo Pulmo know a little about this — to help revitalise their previously unprotected and overfished waters, the Mexican government turned Cabo Pulmo into a national park in 1995. But more controversially, they also banned fishing, a big deal in an area where many residents lived off the food they caught by hand. The preservation efforts paid off, though — researchers say the park experienced a 460% increase in the number of fish living in park waters between 1999 and 2009, turning Cabo Pulmo into one of the world's most robust marine reserves. Now, many residents who once relied on fishing have been able to move into jobs in ecotourism or other vocations supporting the park.