The Edinburgh Triathletes vice-president Andrew McMenigall died after being hit by a lorry in Cornwall during the ride last summer.
Mr McMenigall, 47, from Craigleith, Edinburgh, was killed along with colleague Toby Wallace, 36, hours into a Land's End to Jonn O' Groats fundraiser for the Kirsten Scott Memorial Trust.
The club said the overnight swim on Friday at George Watson's College in the Scottish capital is to remember their efforts and raise funds for the trust, set up in January 2012 after colleague Kirsten Scott died from cancer aged just 25 shortly after being diagnosed.
The trip was said to have had a dual purpose in helping to support wider work in the community for young people with cancer and their families — his daughter had earlier recovered from a brain tumour.
Mr McMenigall had worked as an Edinburgh-based senior investment manager for the global investment firm Aberdeen Asset Management since 2003.
The father-of-two had coached at the athletics club for seven years.