The event, called Sydney Skinny, is to take place at Cobblers Beach, Middle Head on 17 February, and is being touted as the world’s first nude ocean swim.
It costs $35 to enter, and supporters can attend for $15 or $30 for the family. No spectators will be allowed.
Marsh has already been in contact with industry types such as Gruen stars Todd Sampson and Russel Howcroft to ask if they will participate. They are yet to confirm.
Marsh, who is himself taking part, told Mumbrella: “On one hand it is a cheeky, large scale skinny dip in Sydney’s Middle Harbour to raise funds for a national park. But the intention is for this to be so much more than getting your kit off for a good cause.