If writing National Geographic’s new book 100 Dives of a Lifetime: The World’s Ultimate Underwater Destinations taught me anything, it's that the diversity of environments in the water rivals that on land. Although ocean covers more than 70 percent of the planet’s surface, we’ve explored a mere five percent of it.
So for those looking to channel their inner adventurer, our aquatic realms offer abundant opportunity. Yet only some three percent of the ocean is protected, which is why National Geographic works with researchers such as Explorer-in-Residence Enric Sala, who launched the Pristine Seas initiative with the goal of saving the ocean’s last wild places. Here are 21 dive sites spanning the globe that provide insight into the undersea world we’re striving to protect.