The Duchess of Cambridge joined four-time Olympic gold medalist sailor Ben Ainslie and his team on Saturday, boarding a 45-foot (13-meter) catamaran, flying through the water at 38 mph (61 kph).
Her Royal Highness, a keen sailor who beat her husband Prince William in a yachting race off the coast of Auckland in 2014, donned a helmet and strapped herself in for the ride outside Portsmouth in the south of England.
The training session took place on the Solent, a strait of water separating mainland England from the Isle of Wight, and where the original America's Cup race set sail in 1851.
Britain's America's Cup bid
Britain has never won sailing's "Auld Mug," but Ainslie hopes to change all that.
The English sailor launched his own multimillion dollar America's Cup bid in 2014
, with Middleton as the team's royal patron.
Ainslie previously won the Cup in 2013 as a member of billionaire businessman Larry Ellison's Oracle Team USA.
With Middleton on board, Ainslie has been testing one of his team's development yachts -- a foiling AC45 catamaran -- ahead of the Louis Vuitton America's Cup World Series in Portsmouth, in late July.
The two-day racing event is a build-up for next year's America's Cup Challenger series.
All aboard the 'Tech Deck'
Middleton is also a patron of the 1851 Trust, a charity set up by Ainslie's sailing team which provides nautical training and education for young people.
Dressed in a sleek nautical-style shirt and pencil skirt, the Duchess helped open the Trust's new educational center before changing into sailing gear for her ride along the Solent.
The Portsmouth educational center -- called the "Tech Deck" -- features an interactive exhibit on the science behind America's Cup yachts.
As part of the opening, Middleton unveiled a painting of yachts she had created during a previous visit to the Trust last year.