Scientific teams accompanying Lecomte, including NASA, 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.
Ben Lecomte is set to cover 9,000km (5,600 miles) battling giant waves, jellyfish and the "Great Pacific garbage patch" - a large collection of plastic waste in the ocean between California and Hawaii. "Rather than calling it an island of trash, it is more like plastic smog throughout the ocean".
A crowd of around a few dozen people gathered at the beach in Choshi, a couple of hours from Tokyo, to see the swimmer off. Lecomte, wearing a wetsuit and flippers, drew cheers as he set off doing a brisk crawl.
Mercato : l’ASSE vise deux ex-joueurs de l’OM, dont Vainqueur ?
Mais en cas d'échec dans les dossiers des deux premiers, les dirigeants stéphanois auraient une solution de rechange. L'OM réclamerait pas moins de huit millions d'euros pour laisser filer Rémy Cabella du côté de l'ASSE .
It was becoming a father that inspired the Frenchman to take up his cause.
The 50-year-old's plan is to swim for eight hours a day, as well as consume over 8,000 calories, as he undertakes an extraordinary journey that is part-adventure and part-scientific experiment.
This time, he said, he will be wearing a shark-repellent bracelet. "To do that day in and day out, to push you and to push your limits, then the mind has to be super strong".
"To do the physical aspect of it, yea, it is hard, but what is much more hard is to be in that very hostile environment, and the mind has to be super strong", he said.
Harry and Meghan ‘to have Great Tew home’
The ceremony, held in order to celebrate the Queen's birthday, usually sees nearly all senior members of the royal family in attendance.
"When you don't have anything to occupy your mind it goes into kind of a spiral, and that's when trouble starts", he says.
'When I was little and I was with my father walking on the beach, I didn't see any plastic, or hardly any.
And he would know. "Finally ready to start my swim across the Pacific Ocean", Lecomte, who became the first person to swim across the Atlantic in 1998 - in just 73 days - wrote on Twitter. This is far from the first challenge Lecomte has taken up. His words as he left the water?
Nadal perd son premier set depuis trois ans !
Il a mis fin au premier set avec un coup droit qui a abouti sur la ligne de fond, à sa troisième balle de manche. Sur deux jours, Juan-Martin Del Potro écarte Marin Cilic et se qualifie pour les demi-finales de Roland-Garros.