The budget bash, which will cost just £100 per head, is set to take place at a secret location off the south coast.
A group of 20 friends will take part in high-octane water-skiing and speedboat racing during the day and tuck in to a barbeque lunch.
Booze will be banned while the group are near the water but the Prince and pals should make up for it in the evening with a riverside boat pub crawl.
According to The Sun three separate weekends have been booked with a south coast watersports firm specialising in stag and hen dos, so that availability can be guaranteed while the details are worked out.
The company hosts a range of equipment including wakeboards, waterskis, ringos, wake skates and wake surf boards.
Wills and the gang are reportedly staying in a nearby country house for the weekend. The total cost of the party is not expected to exceed £2,500.
A Royal insider told the paper: “The watersports weekend is a perfect option. They can let their hair down without worrying about who is around.”
Clarence House said: “The stag party is an entirely private matter.”