The skipper of the boat Groupe Dubreuil in the Vendee Globe solo non-stop round-the-world yacht race woke up to find his foil broken in rough conditions in the southern Indian Ocean.
Sebastien Simon was in second place overnight but alerted his team that the starboard foil had just broken, forcing him to decrease his sails.
Simon remains 200 nautical miles ahead of the third-placed skipper but is slipping swiftly behind Charlie Dalin, who leads in Macif.
"I was sleeping when the boat suddenly went to the heap and I very quickly realised that something was wrong.
"I went to check on deck and the foil was broken at the elbow," he said.
The race, which takes place every four years, got underway from Les Sables-d'Olonne in western France in mid-November with the 40 skippers embarking on a 24,300 nautical mile course which takes roughly three months to complete.