One of the most difficult adventure challenges in the UK is being attempted by a group from Cornwall.
Three sailors and two runners from RNAS Culdrose and HMS Raleigh are competing in the Magellan Barmouth to Fort William Three Peaks Yacht race.
They must complete 389 nautical miles from Barmouth in south Gwynedd to Fort William in Scotland.
They also climb Snowdon, Scafell Pike in Cumbria and Ben Nevis in Scotland, Britain's highest mountain.
There is 18 miles of cycling, 72 miles of running and 14,000ft of climbing in the race which started at 1500 on Saturday.
Last year the HMS Raleigh team was forced to withdraw through injury.
Now in its 27th year, the Magellan Three Peaks has been imitated as far away as Tasmania and Hong Kong.
But sailing from Barmouth to Fort William, taking in the highest peaks of Wales, England and Scotland, still remains among the toughest tests of mariner and mountaineer in the world.