Fortunately, we know more about the problems that we have than in all preceding history. We know now the consequences of the things that we put into the air, into the water - of the way we treat life on Earth.

With respect to the ocean being the heart of our blue planet: We are often asked, 'How much protection is enough?' We can only answer with another question: How much of your heart is worth protecting?

Globally sharks have been killed for their fins, for their cartilage, for their livers, for their meat. But mostly what has driven some species of sharks to near extinction - including the hammerhead shark - is the new luxury taste for shark fin soup.

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.

I want to get out in the water. I want to see fish, real fish, not fish in a laboratory.

Use your power to do whatever it takes to secure for humankind an enduring place on this little blue speck in the universe - our only hope.