Paris and Doug have been thrown off a boat….

Heiress Paris Hilton and her boyfriend Doug Reinhardt — star of MTV’s The Hills – were forced to walk the gangplank after they were spied swapping spit during an upscale yacht party in Cannes over the weekend.

Nauseated partygoers at the affair — hosted by showbiz legend Elton John — looked on as Paris and Doug’s latest episode of PDA left the lovin’ twosome in more trouble than they bargained for. The couple was asked to leave the boat after the spent nearly an hour having one another’s neck for dinner.

“As soon as Paris arrived she had her tongue down Doug’s throat. Everyone kept saying how inappropriate they were being but Paris didn’t care who was looking,” one furious spywitness told The British Mirror on Sunday. “They got so worked up she dragged Doug below deck so they could have some private time. But as they were closing the cubicle door so they could tear into each other, they were caught out. David spotted them and the captain was furious. He kicked them off for unsociable behaviour. Everyone congratulated the captain.”

Doug and Paris attended last week’s Cannes Film Festival for the premiere of a new documentary based on the socialite’s life. Paris, Not France will premiere on MTV this July.