Half of all rescues were to sailing and leisure boats
RNLI lifeboat crews and lifeguards in Cornwall, Devon and Dorset had their busiest year in 2009, dealing with 12,000 incidents, the charity says.
The RNLI's 35 lifeboat stations across the counties launched a total of 1,648 times, rescuing 1,687 people.
The busiest lifeboat station was Poole, followed by Falmouth in Cornwall and Exmouth in Devon.
Lifeguards on more than 90 beaches also dealt with 10,253 incidents and assisted 12,357 people.
Poole's volunteer crews launched some 200 times, rescuing 242 people.
Falmouth's two lifeboats, inshore and all-weather, put to sea a total of 102 times, while Exmouth's lifeboat station had 95 launches.
Adrian Carey, divisional inspector for the South West, said half of all launches were to sailing vessels and leisure motor boats.
He said: "It's for this reason that the RNLI's volunteer sea safety team work with boat owners to promote simple ideas to help avoid incidents.
"I would urge people to seek their advice and avoid becoming one of our statistics."
The busiest beaches for RNLI lifeguards were Weymouth's main beach with 647 incidents, Perranporth in Cornwall with 608 incidents and Woolacombe in north Devon where the RNLI lifeguards dealt with 577 incidents.
Steve Instance, divisional lifeguard inspector for the region, said it was "extremely busy" when there was good weather.
He said: "People were flocking to the beach, eager to enjoy themselves and this is when high levels of incidents can occur.
"This was particularly notable during the first week of August when a spell of warm weather combined with spring tides and some big surf created tricky conditions.
"Over just one day of this week, lifeguards assisted 222 people and saved nine lives in a number of mass rescues. It was their busiest day on record."