Woody Harrelson cools off in the hot Florida sun with an impromptu skinny dip with actor friend Owen Wilson.

The Natural Born Killers star, 46, has been hanging out with the Wedding Crashers actor in Miami while Wilson films his latest movie Marley & Me.

But while shy Wilson wore regulation swimming shorts, free spirit Harrelson stripped off to his birthday suit as he leapt into the ocean.

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Birthday suit: Woody Harrelson shows off his toned physique as he clambers out of the water

Over the boiling weekend in Miami, where temperatures reached 30C, the pair watched both the men's and ladies' singles tennis finals at the Sony Ericsson Open in Key Biscayne.

On Saturday, the actors had front row seats to watch Serena Williams beat Serbia's Jelena Jankovic, and reclaimed their prime position on Sunday to see Russia's Nikolay Davydenko win against Spain's Rafael Nadal.

After spending hours under the blazing sun watching the centre court action, Harrelson couldn't wait to get back to his Miami waterfront home and rid himself of his sweaty clothing.

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Lift off: Unlike his naturist friend Woody, Owen Wilson wisely decides to keep his shorts on for his swim

After enjoying a dip in Miami Bay, Harrelson climbed out of the Atlantic for a naked work-out on his private dock.

As he hoisted himself out of the water, Harrelson showed his tan wasn't quite all over as he flashed his backside.

Despite his white bits, the 46-year-old cut an impressive figure as he stretched and did press-ups in the nude.

Perhaps he is getting in shape for his upcoming film role in The A Team remake - playing pilot Captain Murdock.

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Butt of the joke: Woody Harrelson shows off his tan lines

Harrelson is well-known for his wild antics and love of partying and has been a vocal campaigner for the legalisation of marijuana.

Admitting his wild behaviour, he said: "Whatever it is, I tend to get into things in an extreme fashion.

"I'm a sensitive soul. Now I feel pretty balanced. But it's not like I don't like to party. I will always like to party, and if that ever changes, slap me.

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Game, set and match: The Hollywood friends check out Russia's Nikolay Davydenko beat Spain's Rafael Nadal at the Sony Ericsson Open in Key Biscayne, Florida on Sunday

"Every day I swim, I surf, climb coconut trees, play with my kids, eat mangoes. There's no form to it, which I kind of like."

Harrelson and Wilson have been friends for many years and last year they holidayed together in Peru and Hawaii.

Harrelson supported Wilson after his attempted suicide attempt last August.

Firm friends: After returning home from the tennis, the two actors are ready to cool off