As a veteran big-wave surfer, Alec Cooke has ridden some of the scariest waves around the world.

But it was during a swim around O'ahu last week that scared him the most.

"There's so much trash and pollution out in the water that people don't know about," Cooke said. "It's a mess out there. It's scary, it really is, because you don't know what's going to happen. Will it get so bad that the future generations can't even go out and enjoy the ocean?"

Cooke, who is 52 and resides in Waialua, completed his around-O'ahu swim on Sunday as a way to raise awareness about near-shore pollution.

Cooke said he swam around 160 miles in 70 hours over 10 days, according to his Global Positioning System. He started on Sept. 5, and swam every day for 10 consecutive days.

"There was a lot of swimming in and out from the shorelines, so it wasn't a straight line around the island," he said. "I trained the whole summer for this, but it was still tough. My body was hurting every night, but I went back out there every morning."

Cooke swam with the aid of a mask, snorkel and fins so that he could get close-up views of the damaged reefs. He said trash could be found virtually the entire course.

"Some of the stuff is amazing," he said. "I saw telephone poles, car batteries ... a refrigerator," he said. "I know some of that gets washed out during flash floods, but it's still out there."

Cooke swam only during daylight hours, and camped overnight at the various stops. An escort boat and support team followed him the entire way.

Cooke said he took water samples from various areas around O'ahu, and plans to have it tested.

"I'd like to see what we can do to bring the environmental organizations together to clean it up," he said. "Because some of it is really bad."

Cooke skipped certain sections of the island, specifically areas that are known to have lots of sharks, or are used by the military.

For example, he did not swim the section from Barbers Point to Pearl Harbor because of the military presence there, and because he said that area is "filthy" with runoff pollution.

"There are some areas where you just can't swim without getting sick, or worse," he said.

When Cooke completed his journey on Sunday, he said he had numerous blisters on his feet and a sore back.

However, he said he'd do the swim again if it leads to a cleaner ocean.

"This wasn't about me. I did this to keep the ocean blue," he said. "Hopefully, I had a chance to make a difference, or at least make a dent."