TOKYO -- Professional distance swimmer Ben Lecomte, 51, set off from Japan to San Francisco on Tuesday in an attempt to become the first person to swim across the Pacific Ocean. Spokesman Alexandre Borreil said Lecomte left at 8 a.m. on Tuesday from Choshi, Japan, which is northeast of Tokyo in neighboring Chiba prefecture. He is expected to swim eight hours daily on a journey that could take six to eight months and will cover about 8,000 kilometers (5,000 miles).

"For the moment we know he left and everything went well," Borreil said.

According to the BBC, Lecomte has spent more than six years preparing, and he has completed a similar swim across the Atlantic in 1998. His training included hours of open water swimming, and "visualization" exercises to prepare mentally. He could face sharks, cold temperatures and storms during the swim.

More than six years of preparations have lead to this moment. Finally really to start my swim across the Pacific Ocean. #theswim #benlecomtetheswim watch the live stream of my departure on @Seeker Facebook. @Discovery pic.twitter.com/TPJlz4tbEY — Ben Lecomte (@BenLecomteSwim) June 4, 2018

He's doing this to raise awareness about the health of the world's oceans and the threat of pollution.

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Scientific teams accompanying Lecomte will collect more than 1,000 water samples and study plastic pollution, mammal migration and the effect of extreme endurance events on the human body. The support boat will have an GPS tracker, and anyone who wants to follow Lecomte's journey can do so on his website.