A "truly inspiring" endurance athlete who died attempting to swim the English Channel will be "deeply missed", his sister said.
Douglas Waymark, 44, was undertaking the solo 300-mile Arch to Arc triathlon between England and France as he began to struggle in the water, around 12 nautical miles from Dover.
The adventurous athlete, who lived in Cheltenham, was a "determined and driven man" who loved mountain climbing, sailing and hiking, according to older sister Jo Ikel.
She said in a Facebook tribute: "He was my brother and one of the most competitive people I know. He would always be the first to try something and then see if he could better it.
"He was a loyal and hilarious friend with a massive friendship group ... he is deeply missed by all who knew him as well as those who have only heard of him."
The Enduroman Arch to Arc challenge sees competitors run 87 miles from London's Marble Arch to Dover, swim approximately 21 miles across the Channel, and then bike 181 miles from Calais to the Arc de Triomphe in Paris.
The website calls it an "extreme event" only for those "experienced in ultra distance events", with proof of long runs, swims and bike rides required to enter.
A tribute on the Enduroman website read: "He touched our hearts with his strength, organisation and quiet humour.
"He had gained massive respect amongst all who knew him. The Enduroman community will miss him and will never forget him."
Mr Waymark, originally from Swansea, also leaves behind a younger brother, girlfriend and parents, Mrs Ikel said.
She added: "His legacy of Be More Doug is fitting for a truly inspiring and much missed chap."