Prince William's Belated Beach Birthday Celebration Danny Martindale/Getty Images Britain's Prince William celebrated his 30th birthday with a belated beach party over the weekend. The prince's birthday was actually Thursday, but the future king apparently spent it quietly. Although Buckingham Palace would not provide details, Prince William's wife, Catherine, Duchess of Cambridge, reportedly planned a low-key dinner with some of his most loyal friends. But William apparently made up for the quiet evening afterward. According to the U.K."s Sun, William had some friends stay with him at a rented cottage in Anglesey. On Saturday, the group slept late, had breakfast and drove down to the beach. "We hear that William actually spent his birthday riding on a doughnut ring behind a speedboat in Wales," said Vicki Arbiter, royal contributor for ABC News. Prince William loves to be a bit of a daredevil. William, and his brother, Prince Harry, donned wet suits and joined their friends in the surf. Wife Kate Middleton stayed on the sand with her sister, Pippa Middleton, and other friends, the Sun reported. William and Kate's dog, Lupo, apparently was with them. "They do love to be outdoors," Arbiter said of the royal couple. They love exercise. They love athletics. They love sport. They're get up and go as a couple. This is a big year for William, and not just because of his 30th birthday. He will reportedly receive an inheritance of nearly $15 million from the estate of his late mother, Princess Diana, later this year. According to Diana's will, which was made public, William and brother Harry are to inherit an equal amount of money, as well as some of her personal belongings, including jewelry, dresses and more.