updated 06/25/2012 AT 10:00 AM ET
•originally published 06/25/2012 AT 10:35 AM ET
Prince William got all wet for his his big 3-0.
Activities included an excursion into the choppy seas off Anglesey, north Wales, where William was pulled across the chilly waters on an inflatable rubber ring by a speedboat – leaving locals abuzz when news of it was leaked to the Sun tabloid Monday.
Some of William’s oldest and closest friends, including Thomas van Straubenzee and Harry Aubrey-Fletcher, were on the island to help celebrate, just as Kate’s sister Pippa Middleton was also believed to be there for the party.
Despite the calendar saying it is summer, the weather was rainy and windy, but a source told the Sun that the foul weather didn’t inhibit the festivities.
“For most 30-year-olds,” said the source, “the last thing they would want to do is freeze themselves on a wet weekend in Wales. But this is typical of William.”
The group then headed to the couple’s rented farmhouse for a birthday dinner.
The couple spent much of last week based at Prince Charles’s country home Highgrove house, Tetbury, Gloucestershire, so William could take his RAF helicopter course nearby. On Wednesday, Kate was spotted shopping in the local village.
William, who upon turning 30 inherited $16 million from his late mother Princess Diana, is reported to have received a specially-designed watch from Kate for his birthday.