American eye-ful! Ryan Seacrest grabs his crotch and flashes his bare bottom during party cruise with pals along Italian coast

As the host of American Idol, Ryan Seacrest is usually more reserved and well-mannered but this was a wild side that's not often seen.

The 40-year-old entertainment mogul shed his clean-cut image and revealed his inner party boy on Wednesday while cruising down the Italian coast off Portofino with Chris Hemsworth, 31, and girlfriend Hilary Cruz, 26, among others.

Ryan was really letting loose aboard the private yacht where he was seen grabbing his crotch with a mischievous grin and swigging wine right from the bottle, before flashing his bare bottom after diving into the water.

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The TV host, whose net worth tops $330 million, was rocking the frat boy look in cargo shorts and light-coloured shirt buttoned down the chest with rolled up to the elbows.

He grinned beneath the brim of trilby hat while standing by the railing of the middle deck.

And then surprisingly, Ryan grabbed his crotch while directing his mischievious gaze at someone standing below.

The drinks were going down smoothly too from the look of things.

While chatting with his pal Chris 'Thor' Hemsworth, who was on board for the ride with his wife Elsa Pataky, Ryan must have had a terrible thirst.

Ryan was holding a bottle of wine, tipped it back and proceeded to drink it straight from the bottle without a glass which is the usual norm.

It looked like a nice bottle of rosé but with Ryan's reported $65 million annual salary he can drink it anyway he pleases.

As if Ryan's crotch grabbing and wine-guzzling weren't enough to raise eyebrows, his host with the most behavior was spiked with an enthusiasm not seen on American Idol.

The 5 ft 8 producer appeared to make sure everyone on board the cruise ship was comfortable. 

As the group dined and drank on the top deck, Ryan went around the group chatting and even stopped to give a guy a shoulder massage.

Ryan was clearly the life of the party, laughing, goofing around and generally acting like a kid at heart.

Hemsworth was similarly attired in white button down shirt, cream-coloured trousers and trilby hat.

The strapping 6 ft 3 Australian towered over Ryan as they cracked jokes together and when he wasn't playfully sparring with the TV host he was cosying up to his wife Elsa. 

Ryan, meanwhile, looked like a smitten school boy the whole time around his new former Miss Teen USA squeeze..

Later the twosome took the party into the water- and Ryan almost left something in there.

As he climbed back onto the yacht his trunks slipped down giving everyone a look at his white bits.

Hilary was a bit more careful with her bikini as she jumped aboard a jet-ski, strapping on a life-vest to be sure. 

As she circled the boat, her man preferred to stay submerged, using a personal propulsion device to fly around in the water.

Afterwards they climbed back aboard the yacht for another bout of sunbathing.

Ryan relaxed in a white T-shirt and grey shorts with a dark blue baseball cap and shades.

Hilary made sure she avoided the white bits Ryan displayed and had much more skin toasting in the sun, looking stunning in an aquamarine bikini.

Seacrest has only been dating the former beauty queen for two months but they've certainly hit it off.

The couple jetted in from Los Angeles on Sunday, and have been having a blast on the yacht ever since.