You probably weren't aware there was an underwater cycling world record, but there is, and it's been broken, by none other than a pair of ex-Royal Marines.
It's unlikely to have done their bike a whole lot of good, but Chris Sirett, 54, and Brian Stokes, 40, slipped into wetsuits, donned oxygen tanks and in a tank full of water rode on a turbo trainer for 15 hours - covering 100.13 miles.
Quite the advert for the elite Royal Marines recruitment Stand at the PSP Southampton Boat Show on Saturday.
The funds raised on behalf of charity Commando 999 go to the Royal Marines Association.
Mark Scoular, founder of Commando 999 told the Huffington Post: “As with any world record attempt as physically demanding as this, safety is always a priority.
"So, at 3:38am after a solid 15 hours underwater, the attempt was bought to an end after being deemed too dangerous to continue by the safety team. The divers were lightheaded and suffering from vomiting and nausea.
"However, Chris and Brian have set the World Record for the furthest distance cycled underwater. They have raised thousands for the Royal Marines Association and we are very proud of them.”
After an unpromising start, having to be bribed by her parents to learn to ride without stabilisers, Sarah became rather keener on cycling in her university years, and was eventually persuaded to upgrade to proper road cycling by the prospect of a shiny red Italian bike, which she promptly destroyed by trapping a pair of knickers in the rear derailleur. Sarah writes about about cycling every weekend on road.cc.