A French pensioner has set out to cross the Atlantic inside a large barrel he has built from reinforced plywood, hoping to arrive on a Caribbean island within three months using only ocean currents to carry him along.

"The weather is great - I've got a swell of one metre and I'm moving at two or three kilometres an hour," Jean-Jacques Savin said shortly after leaving shore on Boxing Day from the island of El Hierro in the Canaries.

"For the time being my capsule is behaving very, very well and I've got favourable winds forecast until Sunday," he added in a phone interview.

The three-metre long orange barrel that will be home to the 71-year old former parachutist for the coming weeks has a six-square-metre living space that includes a kitchen, sleeping bunk, chart table, and storage.

Mr Savin built the vessel, which looks like a space capsule, himself over several months in a small boatyard in Alès in the Arcachon basin in southwestern France.