The owner of the silver Peugot 307 got a shock when he returned to find it engulfed in water up to its roof by the incoming tide at Dunbar harbour, East Lothian.
The owner of the drenched vehicle, from Dunfermline, Fife, had been delayed after his own sailing boat had broken down and he had to be rescued by the local lifeboat crew.
Gary Fairbairn, coxswain of Dunbar RNLI, said his crew was called out to rescue the driver at around 1pm on Saturday.
Gary said: "The car owner unfortunately left his car on the harbour slipway while he went for a spot of fishing.
"We were called out to look for him after his car had been reported to the police. We managed to locate the man in his boat just off Dunbar, he had broken down, but we didn't have the heart to tell him about his car until we got back to land.
"To say he wasn't happy is an understatement. We managed to pull the car to safety by using ropes to haul it ashore. But I'm pretty sure it will be written off."
The watery mishap has been shared hundreds of times online and jokers on the Heart of Dunbar Facebook page have been quick to poke fun at the car's owner.
David Hingley, head of visitor services at Hampton Court in London, who was trying to spot seals, tweeted an image of the unusual visitor to the waters, adding sardonically: "Not a seal".
Alan Hardwick said: "I think the engine is flooded."
Douglas Turnbull added: "Not an ideal plaice to park - basking for trouble if you ask me."