Lenning is 34 years old. He has done a few of these, but this one had to be the most challenging. He started early in the morning and completed the swim by 10 p.m.
Lenning trained for over a year.
He and the Bay Area group The Night Train Swimmers left Tuesday at 6 a.m.
First he had to deal with the tides and currents along the 30-mile stretch of shark infested waters. If they had spotted a great white, the plan was to immediately get him out of the water.
"From what I know about great whites, they'll come in and give you a test bite," Lenning joked.
He swims without a wetsuit but applies plenty of grease to retain some of the body heat. During his swim he ran into a school of jellyfish darker and bigger than your typical jellyfish.
"One had come up; I took a stroke and it wrapped around my arm and it got me and when I came back on my stroke it landed on my leg," Lenning said.
But fortunately the cold waters of the ocean helped numb the pain of the sting.
"It was overcast so that was nice, but when it's blue sky, it'll melt you," he said.
Lenning eats every 30 minutes -- a protein drink, carbs and plenty of water. He says he is successful because he is laser focused and doesn't worry about what may be swimming beneath him.
"The Farollones, it's a very special place, if you don't stay calm that stress will wear you down," he said.
That's why now only three people have done it; the last in 1967.
He was just about 800 meters from the shore when he got stuck in an eddy.
"It took 45 minutes for us to break through that," Lenning saud,
By then it was almost 10 at night and dark and foggy. But he made it.
"This one was the biggest one I've ever done," Lenning said. "The mystic of it, the cold and the magical islands off the coast."
He has done 11 swims so far around the world. After swimming this stretch he is now considered one of the best marathon swimmers around. It's hard on the body, so he says he may do this for two more years.