PENLEE Lifeboat was called out to rescue a yacht in heavy seas 10 miles south of Newlyn.
As storms raged and in howling wind, the all-weather lifeboat the Ivan Ellen was launched at around 3pm on Thursday.
It is believed the yacht had run over its sail and would need towing back to Newlyn, which could take several hours.
A spokesman for the RNLI described the sea conditions as "extreme".
"The sea conditions are horrendous," he told The Cornishman. "It's a south-easterly, around 8-9 knots and very rough out there.
"The crew have made contact now and will be trying to get a tow together."