[National Geographic has recently begun their Ocean Now expedition to Cocos Island and the Gemelas Seamounts west of Costa Rica. We've invited National Geographic explorer Sylvia Earle to author this guest post to share stories about her submarine dives on the DeepSee to coincide with the update to our Ocean Expeditions layer, which features this expedition. --Ed.]

LatLong: 5 degrees 33.424 minutes N, 87 degrees 2.489 minutes.

I’m here near Cocos Island five degrees north of the Equator in the eastern Pacific with a National Geographic Ocean Now project involving two ships, the Hanse Explorer and the Argo. I’m on board the Argo, which has a beautiful little submarine called the DeepSee. On the surface, there’s a support boat that’s called the TopSee.

We’re all having a lot of fun out here, and accomplishing a lot of good scientific observations—actually, a few breakthroughs! We were able to go out to two seamounts that have never been looked at with a submarine before. You can’t dive them, because they’re too deep.

The only way they’ve been sampled before is by fishermen. There’s plenty of evidence of that, because during the four dives that we made on them during the past week, we could see literally miles of fishing line wrapped around and around and around these beautiful undersea mountains.

We even saw a big grouper that had a hook still attached in its mouth, and a long line that had been there so long that growth was on the line. He was an awfully skinny grouper, because I think he had trouble feeding. It really breaks your heart to see what happens when derelict fishing gear causes problems for the creatures here. Not just those immediately caught, but those that suffer beyond the time of the fishing.

Generally, though, it’s good news: we have seen lots of fish, corals that are recovering from El Niño years when much of the coral dies. Here’s the thing: During the last strong El Niño, about 90 percent of the coral here at Cocos died. Jorge Cortés, the chief Costa Rican scientist on this ship, who has studied this area for many years, points out that if 90 percent of a rain forest died, people would be up in arms. They would be so concerned! When 90 percent of the coral reef dies, people are concerned, but they don’t react with quite the same passion that they do when something on the land happens that everybody can see.

Underwater, our job partly is to demonstrate the problems that are occurring, and why it matters to everybody—why what happens to the ocean affects you wherever you are, and also how what we do affects the ocean in a way that is important for us to understand. The ocean gives us the oxygen we breathe. Most of the oxygen we inhale comes from the sea. The water that falls out of the sky largely originates in the sea. So you don’t have to be living by the sea to be living by the sea, because the sea really governs life, everybody’s life. It’s really important for us to understand that, so that we can do a better job of taking care of the ocean that takes care of us.