Swiss skipper Dominique Wavre looks set to become the eighth sailor forced out of the Vendée Globe round-the-world ocean race after a key part of his keel broke.
Wavre contacted his shore crew on Friday to inform them of the breakage, which organisers described as "threatening the solidity of the hull bottom and hence the boat's integrity".
If Wavre loses his keel the boat could capsize. A report on the race website said Wavre was considering abandoning the boat but was working with his team to find another solution.
Wavre has reduced sail and will try to sail at a slower speed towards the Kerguelen Islands in the South Indian Ocean, hoping to arrive at the Bay of Morbihan around 9am GMT on Saturday.
The Vendée Globe, a single-handed race for men and women without any stopovers, set off from Les Sables d'Olonne, France, on November 9 into strong winds and rough seas.
Thirty Open 60 race boats – hi-tech carbon fibre yachts built to be fast yet tough – began the race, including two Swiss: Wavre and Bernard Stamm. Seven have been forced to retire due to damage.
The race takes the fleet around the three great capes – the Cape of Good Hope, Cape Leeuwin and Cape Horn – marking the southern tips of Africa, Australia and America.
France's Jean-Pierre Dick currently leads the fleet, with Briton Mike Golding in second place.