He probably thinks he's doing the channel, I don't doubt that
Isn't from what I can see:
Regenerate are Kayaking from the Source of the River Thames all the way to the Sea and then cycling from London to the Pyrenees Mountains.
On the 24th of May of group of us will be Kayaking the length of the River Thames. Starting at Cricklade, we will kayak over 215 miles through Reading, Oxford, Windsor, Putney, and Westminster, ending at Southend pier. This gruelling journey will take ten days of hard kayaking to travel from the source of the Thames to the North Sea and we will be camping out each night along the banks of the river.
https://www.justgiving.com/fundraising/nahwand-jaff
A group of people rowing 20 miles a day downstream and camping during the warm end of May/ start of June isn't anything to write home about.