Eating wildlife is probably not the smartest thing that we can do in terms of maintaining the integrity of natural systems.

When I first ventured into the Gulf of Mexico in the 1950s, the sea appeared to be a blue infinity too large, too wild to be harmed by anything that people could do.

Ice ages have come and gone. Coral reefs have persisted.

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.

I find the lure of the unknown irresistible.

If Darwin could see what we now see, what we now know about the ocean, about the atmosphere, about the nature of life, as we now understand it, about the importance of microbes - I think he would just beam with joy that many of the thoughts and the glimpses of the majesty of life on Earth that he had during his life, now magnified many times over.

Sharks are beautiful animals, and if you're lucky enough to see lots of them, that means that you're in a healthy ocean. You should be afraid if you are in the ocean and don't see sharks.