A "freak wave" caused by the gale-force winds during Storm Aiden capsized a 34ft (10m) yacht, the coastguard said.
A man was rescued after getting into difficulty six miles south west of the Isles of Scilly, with severe gale force nine winds in the area.
Falmouth coastguard received a distress signal at about 05:00 BST.
The lone yachtsman was uninjured and his stricken sailing vessel was towed to safety by the St Mary's RNLI lifeboat in "challenging conditions".
Ian Guy from the coastguard said: "The yachtsman described being hit by a large freak wave which capsized, rolled and disabled the vessel and with a such a severe gale forecast for the area this morning, it was important to get assistance out to this small sailing vessel quickly."
Paddy Cochrane from Falmouth coastguard confirmed in the last 24 hours of stormy conditions they had dispatched lifeboat crews from all over Cornwall, the coastguard helicopter and multiple lifeguard rescues on beaches.
He said: "It's people going down to have a look at the large storm conditions, wave watching and what have you."
Mr Cochrane said he could "guarantee" they would have a further rescues through the weekend, caused by "people making silly mistakes and getting far too close to very, very dangerous conditions".