NEW YORK -- Off the coast of Japan on Tuesday, 50-year-old Ben Lecomte started a journey unlike any other.

"I am looking forward to the big crossing," he said.

That doesn't even begin to cover it. Lecomte, a Frenchman now living in Texas, is attempting a six-month, 5,600-mile swim across the Pacific Ocean to San Francisco. It's a long awaited bookend to his prior swim across the Atlantic two decades ago.

Ben Lecomte Reuters

"I knew I was going to come back to that project eventually," Lecomte said.

Already 11 miles in, Lecomte will be swimming right through a migration area for great white sharks. But it's the danger the planet is in that's on Lecomte's mind, issues like climate change and pollution. He designed his route to pass through a collection of micro-plastic refuse roughly the size of Germany, France and Britain combined.

"I remember times when we would go on the beach and walk and never see any plastic," Lecomte said. "Now, everywhere I go on the beach, I see plastic everywhere."

He plans to swim eight hours at a time, eating 8,000 calories a day and resting each evening on a support boat. If he makes it, he'll be the first to swim the length Pacific.

"To do the physical aspect of it, yea, it is difficult, but what is much more difficult is to be in that very hostile environment, and the mind has to be super strong," he said.

Lecomte is shaking off any personal threat. More important, he says, is drawing attention to the far greater peril facing the planet.