Prince Harry has planned a day of extreme watersports for his brother William’s stag do, The Sun reports.

And before your smutty mind runs away with you, the tabloid reported: “The royal groom to be and 20 pals will enjoy a day of off-shore thrills and spills, racing speed-boats and water-skiing”.

Alcohol will not be permitted during the activities, but apparently the day’s high-energy action will be followed by a pub crawl to venues accessible only by boat.

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The palace refuses to confirm plans for the stag party of William, 28, who will marry Kate Middleton, 29, on April 29 at Westminster Abbey.

“The stag party is an entirely private matter,” Clarence House has said.

However, reportedly the facilities of a specialist watersports firm operating on the British south coast have been booked for three separate weekends, to allow flexibility on dates.

William and his crew are expected to stay at a nearby country estate owned by a friend, with the plans meeting his reported hopes that the event not be too lavish and that it be as private as possible.