Kate Middleton and Prince William relax in matching outfits at the America's Cup

The Duchess of Cambridge proved that the a classic skinny jean is still the best way to dress down.

The Duke and Duchess of Cambridge hit the open seas yesterday afternoon to bring some Royal support to Sir Ben Ainslie's America's Cup team and cheer them on to victory during the Louis Vuitton America's Cup World Series.

Joining the thousands of spectators who came out in support of Sir Ben's Land Rover BAR team, the Duke and Duchess of Cambridge proved that a little 'his 'n' hers' dressing was still acceptable for a laid-back Sunday as they relaxed on a high-speed catamaran, accelerating at over 40 knots over the course of the afternoon.

The royal couple were dressed in matching shirts from Ben Ainslie's Olympic Champion's team, which were printed with official titles on they back, as well as matching dark jeans. Prince William opted for a classic straight leg dark denim, while Middleton relied on her trusty black skinny jeans.

Known for recycling her favourite accessories and shoes, the Duchess arrived wearing her Monsoon nude espadrille wedges which originally retailed for £45. Her jewellery was of a slightly higher price, as she added a pair of diamond pave earrings by British jeweller Kiki McDonough costing £2200, but these have also been seen before.

kate middleton portsmouth — Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive for a visit to the Land Rover BAR at the America's Cup World Series Chris Jackson/ Getty

Middleton has relied upon a sturdy wedge shoe time and again, and wore her Monsoon pair before while on her Royal tour of India and Bhutan and also wore a slingback wedge design for the trip earlier in April.

The royal later swapped her wedges for a pair of Adidas Pure Boost trainers (£54) as she took to the boat for a high-speed trip. By this stage she mirrored Prince William fully, as he already sported a pair of red Adidas trainers. The couple also wrapped up in matching waterproofs, fleeces and caps as they sat aboard the Land Rover BAR viewing boat.

Prince William and Kate Middleton — The Duke and Duchess watched the races from a twin-engine catamaran AFP/Getty

Despite the constant stream of official engagements, it is always refreshing to see the couple looking laid-back in everyday clothing. While we have seen the Duchess in skinny jeans many times before, when she matches up with William in the same outfit, there is something overtly relatable about the pair.

None more so than when, once back on dry land, Kate and William met a group of aspiring sailors from the 1851 Trust – of which Kate is a patron of – with the duo blending in well with the group.