(CNN)May 9 is indelibly inscribed in the mind of Iain Percy.
On Saturday it will be exactly two years since he cradled his dead best friend Andrew "Bart" Simpson in his arms -- two years since he had to steady himself and break the awful news to the sailing star's wife Leah, on what was her 35th birthday.
Not a day goes past when Percy does not think of Simpson -- "he's there every day" -- and he makes no secret of the fact he is still haunted by that tragic accident in San Francisco Bay.
"I don't think it will ever leave me," the British yachtsman tells CNN. "I lost someone that was close to me."
The pair had been inseparable from the moment they first played together in a sandpit aged seven, winning Olympic gold and silver in the two-man Star class at Beijing 2008 and London 2012 respectively before moving up to bigger boats.
But tragedy struck in a training exercise ahead of the 2013 America's Cup, for which Percy was skipper of Swedish entry Artemis Racing.
The 72-foot catamaran capsized and broke into pieces. Crew member Simpson was trapped under the hull for 10 minutes, and attempts by Percy and others to resuscitate him proved unsuccessful.
For Percy, though, Simpson lives on -- his past words of wisdom help with virtually every decision he makes, and it is for his friend that he sails on, plotting to win sailing's most prestigious event with Artemis in 2017.
His syndicate is, on paper, one of the strongest challengers to Team Oracle USA's title defense in Bermuda. And every time they go sailing, a ribbon is attached to the vessel in remembrance of a man cut short in his prime at the age of just 36.
"On a personal level, it's not easy although it's nothing compared to what Bart's family had to go through," Percy says. "I think of them first. But of course I'm driven by his memory, sometimes unhealthily, but being on the water is nice escapism.
"Right now, I'm still working through this. On a personal level I miss him quite a lot as he was a friend, but he was a professional partner too. He always had the ideas.
"Take the Olympic sailing and the technical side of things -- nine out of 10 times the ideas came from him.
"I used to dither, but that's changed. I've listened to him every time we've sailed for so many years, heard his philosophy of racing. So every time that I race, he's still in my ear.
"My decisions in some ways are Bart's as I know what he would have done."
Simpson had only been involved with Artemis for a few months but brought an energy with him that Percy is adamant has kickstarted the team's 2017 campaign.
After the accident, Artemis forfeited its round-robin matches in the 2013 challenger series but returned for the semifinal. Though soundly defeated by Italy's Luna Rossa, the main aim was getting the mourning crew back on the water.
"We wouldn't be where we are if he wasn't who he was," says Percy, now 39. "Bart along with Nathan Outteridge and his crew arrived with this Olympic spirit, if you like. Money was no motivator for them, it was just about winning and that passion for sailing. Bart could just tackle any issue."
That Olympic spirit was first born in the buildup to the 2000 Sydney Olympics in the flat that Percy and Simpson shared with future sailing legend Ben Ainslie.
Simpson missed out on selection in the Finn class to Percy but played a key backup role as both of his flatmates celebrated with Olympic glory -- and Ainslie would go on to win three more golds.
"It was a great time, we managed to play hard and work hard," Percy recalls. "We'd have fun but every day we'd still drive each other on and kick each other out of bed to get to the gym."
The trio were inexorably linked throughout their sailing days, and it is befitting that Ainslie and Percy are going head to head in the America's Cup.
Ainslie, who had brief spell as tactician with Team New Zealand in 2005 and was later involved in a short-lived British syndicate, now heads his own self-named operation. It has royal backing and technological support from the Red Bull Formula One team.
Percy famously once described Ainslie as the "most competitive man in the world," but is looking forward to taking on his good friend at the highest level.
"The America's Cup can be seriously cut-throat so it's nice to have someone like that there," explains Percy. "We're competitive but we have our boundaries and we don't cross those.
"I'm really pleased for him as a friend, as I know it's incredibly difficult to start off a team and get the funding -- the challenge is huge. And it's great for the UK as well. So on a personal level I'm delighted he's there.
"But once we're on the water, of course I'll be doing everything to beat him."
One subject they will regularly discuss is Simpson, who is never far from their thoughts or conversations.
They have been united in their work for Bart's Bash -- billed as the largest sailing event in the world, last year it brought more than 30,000 people together on the water, raising more than $550,000 for the Andrew Simpson Foundation. The charity helps transform the lives of young people through sailing.
The three amigos may now be down to two, but Ainslie and Percy have worked tirelessly with Simpson's family and friends to ensure he is never forgotten.
"I've not been surprised by the warmth to Bart's Bash as he was loved by so many people," says Percy. "We're introducing a 'Bart's buddies' scheme this year to introduce new people to sailing as well, plus it raises money for good causes. It's all the values that were important to him.
"He would try to help anyone. I remember sharing a room with him and it's late and he's tapping away on the computer. I'd be like, 'What are you doing?' and it'd turn out he'd be emailing some young sailor that had a problem -- even though Bart had to race early in the morning. That's just Bart all over, and I miss him."