CAST off your clothes and your inhibitions - it's time to get naked.

The cheekiest swim event in Sydney is on again at Mosman's Cobblers Beach on February 23.

The only requirement to take part is a ticket and a willingness to leave your clothes on the beach and swim in the nude.

Billed as the world's large nude ocean swim, the Sydney Skinny is designed to celebrate the human body.

Organiser Nigel Marsh, said the community swim aims to combat the perfect body image.

"It's a chance to be utterly authentic and stick two fingers up at all those ludicrous, airbrushed images of bodily perfection in the magazines,'' he said.

The idea for the event came to Mr Marsh after a naked splash at Obelisk Beach. The author and co-founder of Earth Hour said he felt "reborn'' after swimming in his birthday suit and decided Sydney needed a mass skinny-dip.

"Just imagine how joyous an experience a bare-butt communal swim in the world's most beautiful harbour would be.''

media_camera Participants in the first Sydney Skinny, which attracted about 100 people last year.

The mass skinny dip was held for the first time last year and attracted nearly 1000 bare bodies of all shapes and sizes including an 89-year-old and a paraplegic.

"There was an 89-year-old chap who was beaming from ear to ear, a man who had flown in from Kansas, and a woman who used it as a final line in the sand after years of suffering from an eating disorder,'' he said.

"So many people thanked me for pushing them out of their comfort zone.''

There are two swim distances - 300m and 900m, and both are untimed and in calm waters. Flippers and flotation aids are allowed.

If the thought of getting naked in front of strangers inspires panic, Mr Marsh said swimmers could slip out of their bathers in the water and sarongs would be handed out to help keep privates private.

The swim will raise money for rejuvenation projects in Sydney Harbour National Park and conservation work by National Parks and Wildlife.

Last year's event raised about $15,000 towards Middle Head's walkway project.

Only participating swimmers will be allowed on the secluded beach while the festival area on the headland is open to everyone.

To buy a ticket visit the sydneyskinny.com.au