Some experts look at global warming, increased world temperature, as the critical tipping point that is causing a crash in coral reef health around the world. And there's no question that it is a factor, but it's preceded by the loss of resilience and degradation.

When I arrived on the planet, there were only two billion. Wildlife was more abundant, we were less so; now the situation is reversed.

Never again will we have this good a chance as we now have to find an enduring place for ourselves within the natural systems that keep us alive. It's a sweet spot in history. That's why this is such a critical time.

I have lots of heroes: anyone and everyone who does whatever they can to leave the natural world better than they found it.

We need to respect the oceans and take care of them as if our lives depended on it. Because they do.

Santa Monica Bay is less polluted today than when I first moved to the area in the 1970s, because actions have been taken to avoid putting some of the noxious materials into the sea. I think people are more aware than they once were, the air is cleaner, water generally is, in spite of the fact that there are more people.

I've spent thousands of hours under water. And even in the deepest dive I have ever made, 2.5 miles (about 4 kilometers) down, I saw trash and other tangible evidence of our presence.