The Duke and Duchess of Cambridge will cheer on sailor Sir Ben Ainslie and his crew as they race in the America's Cup World Series.
Sir Ben, the most successful sailor in Olympic history, will skipper his team as they compete for the second day in the opening leg of the series, being staged in waters off Portsmouth.
William and Kate will today leave their children - Prince George and Princess Charlotte - in the care of their personal staff and travel to the South coast for the event.
The Duchess, who is a keen sailor, joined Sir Ben in June last year when he formally launched Britain's bid to win the America's Cup for the first time.
She is a committed supporter of the sailor's team BAR (Ben Ainslie Racing) and is also royal patron of the 1851 Trust, which works to inspire the next generation through sailing and the marine industry.
The America's Cup is international sport's oldest trophy, first staged in 1851 off the Isle of Wight, but it has not returned to British waters following that inaugural defeat.
Sir Ben, who has won four Olympic golds and a silver, was famously employed as a tactician during the last America's Cup race, helping the US Oracle team overturn an 8-1 deficit to beat New Zealand.
Points collected during the World Series determine who will challenge the US for the America's Cup which will be staged in Bermuda in 2017.
And Sir Ben is off to a flying start after his crew clinched a win and a second place during the two races staged yesterday in front of thousands of spectators.
During the visit the royal couple will tour the team technical areas before the day's racing begins and meet the six international team skippers and their crews from USA, France, New Zealand, Japan, Sweden and Britain.
William and Kate will also tour the BAR team base to see their state of the art facilities and meet staff and families. Later they will take to the water to watch the first race of the day then return to dry land to see the second.
Before presenting medals to the winning teams they will tour the Waterfront Festival Arena with its many interactive nautical displays.