During one swim, Lewis Pugh saw his support boat crew screaming at him just before they hauled him from the water as a sea lion bore down on him. During another, the air temperature dropped so far below freezing that a wave broke over the crew and froze solid.

An extreme swimmer from Britain, Pugh this month ended a series of swims in the ocean near Antarctica, including the two southernmost swims in history. And during it all, he wore nothing but a skimpy Speedo bathing suit, a cap, and goggles.

He said he swam to show his support for the creation of a marine sanctuary in Antarctic waters. The idea of setting aside an area of the Ross Sea in which fishing is banned has been promoted by the governments of the U.S. and New Zealand and is supported by most of the 24 nations and the European Union that govern fishing in the region.

But each time the plans have come up for a vote, they have fallen short of the required consensus due to one or two dissenting nations with Antarctic fishing interests, including Russia.

So after finishing the swims, Pugh last week traveled to Russia, where he met with Russian Defense Minister Sergei Shoigu, in the minister's role as president of the Russian Geographical Society. Pugh said he felt there was "an appetite for dialogue" among Russian officials.

He said he plans to travel soon to Washington to continue his campaign.

So how did swimming in Antarctic waters feel?

"I could say I love it, but nothing could be further from the truth," Pugh said.

He said he has never been more terrified than during his swim in the Ross Sea's Bay of Whales, in which the seawater was as cold as it can get before it freezes and the air temperature had plummeted to minus 37 Celsius (minus 35 Fahrenheit). He said his fingers were in agony and turned completely white. After each of the swims, he said, he took a 50-minute shower to defrost.

Originally Pugh had planned five Antarctic swims of 1,000 meters (1,094 yards) each, but the extremes of the region forced him to cancel one of the swims and pare back the others.

Two of the swims he completed were 500 meters, taking about 20 minutes each. He swam about 350 meters in the Bay of Whales and 200 meters in the first swim near Campbell Island, he said, before the sea lion cut it short.

Pugh, 45, began long-distance swimming at age 17. He said he feels the environment is a huge issue for this generation and he plans to keep pushing the boundaries with his swimming to highlight the need for conservation. In 2013, he was named Patron for Oceans by the U.N. Environment Programme.

Andrea Kavanagh, the Antarctic and Southern Ocean campaign director for The Pew Charitable Trusts, which has also been promoting the idea of a Ross Sea marine sanctuary but wasn't involved in Pugh's swims, said she thought the Brit's efforts could only help.

"Any kind of outreach to Russia is a good thing at this point," she said. "I don't think it got any coverage there before, and he's helped bring it into the news cycle."

Kavanagh said that on a personal level she's been riveted by Pugh's swims.

"I can't believe he did it, it's truly astonishing," she said. "What the human body can endure is fascinating."