The pair hit the water at the London Aquatics Centre last week in a bid to find the King or Queen of the pool. Would it be Britain's Got Talent judge David? Or would Olympian and I'm A Celebrity... Get Me Out Of Here favourite Rebecca take the crown. (As you might expect!)
Sadly, we won't know as they weren't technically racing, more just swapping tips and having a bit of fun. (We'd put our money on Rebecca, though. Sorry David!)
Putting competition to one side, David spoke fondly of Rebecca, saying: "Training against Becky today was a bit nerve-wracking as she's such a swimming icon. It was a case of sink or swim so I think I gave it my best shot!"
The pair donned their swimwear in a bid to promote British Gas SwimBritain, a programme trying to get us Brits back in the water and start racking up those lengths.
Becky, who retired from competitive swimming last year, joked: "I will always love being in the water and a challenge like British Gas SwimBritain is brilliant as it's really inclusive – not just for professional swimmers, as David proved today!
"Joking aside, swimming offers everyone a full range of health and fitness benefits so the more people we can encourage to swim regularly, the better. It's a full body workout without any stress on the joints. A gentle half hour swim can burn up to 200 calories."
There are two challenges available for the fitness fans out there – SwimBritain1000, a four-person relay where each team member swims 250m four times and SwimBritain500, the same course but a shorter length of 125m.
David and Becky also carried out a fitness test on dry land which you can check out here and carry out in the comfort of your own home... If you're brave enough!
Watch the pair discuss the challenge here:
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