Marine biologist, diver, and environmentalist Sylvia Earle has dedicated most of her life to exploring our oceans. But even after logging more than 7,000 hours underwater, she says there’s still a lot that remains undiscovered.  “The deeper you go in the ocean, the less we know,” she said at the TIME 100 Climate Leadership Forum on September 24. “It's like diving into the history of life on Earth.” At 90, Earle has seen parts of the ocean most people will never see, and currently holds the