In a remote corner of the sea nearly untouched by the tide of time, Cuba's Gardens of the Queen (Jardines de la Reina) marine park is home to living things that have virtually vanished from the rest of the Caribbean.

I'd been there before, in 2000, but I didn't know what to expect after 16 years. Our team desperately wanted to explore the park's elkhorn reefs. The fast-growing coral is now extremely rare and critically endangered, with 90 percent gone from most of the Caribbean. How well had these reefs survived as other populations perished? (See more about Cuba's marine reserve in a story by Hayes and her partner, photographer David Doubilet, in the November issue of National Geographic.)

We headed