Kate, 32, an avid sailor herself, attended a brunch for the America's Cup yachting team in Greenwich, London, and was introduced to the athletes and their fans by Olympian Sir Ben Ainslie.
On a sunny morning by the River Thames, Kate, in a white Jaeger dress and navy pumps, met boat designers and sailors chasing the oldest sporting trophy in the world.
"She's from a sailing family, and she loves sailing," said Lord Michael Grade, who launched the bid. "You can just tell she's always been keen on it, and her face just lights up when she's talking about it. You can tell by her eyes sparkling that she is very passionate about it."
Ainslie, 37, who won medals at five straight Olympics from 1996-2012, including four golds, said the team would like to take Kate out sailing in the future.
"She was asking lots of technical questions – she knew her stuff," he said. "We were all sharing sailing stories, and I think her sailing comes from her family. It means a lot to have her here."
One of the yacht designers, Simon Schofield, told PEOPLE that Kate was eager to hear all the technical details as they looked over a smaller, 45-ft. version of it. "She seemed really excited," he said. "Hopefully she'll go out on the yacht one day."
The fashion-forward duchess also complimented a sailor on his eyewear after they met. America's Cup sailor David "Freddie" Carr sported Buddy Holly-style thick-rimmed spectacles, and they promptly caught Kate's attention.
"She said my glasses were a good look," a beaming Carr told reporters. "I can die a happy man."
Carr, who is a member of Ainslie's planned team for 2017, also tipped his hat to the duchess's sailing prowess – in April, she memorably beat husband William in some races in New Zealand.
"She was down in New Zealand in Auckland sailing with their team on the New Zealand America's Cup yachts and did very well," he said. "If Ben's not up to the job, we'll get Kate."
Kate's Birthday Surprise for Prince PhilipRounding out the duchess's busy day was a tea party in Queen Elizabeth's back garden.
Wearing a pale peach Alexander McQueen dress, Kate feted Prince Philp on his 93rd birthday.
In the beautiful London sunshine, she, the Queen, 88, and Philip mingled with some of the thousands of guests who enjoyed tea and cakes on the Buckingham Palace lawns. It is one of three garden parties that Her Majesty hosts at the palace each summer.
Also in attendance: Princess Eugenie, 24, her father Prince Andrew, 54, and Princess Anne, 63.