[sandworm101]

>> is Michael Phelps (or whoever) faster on it?

Nope. He would be horrible with this device. That would be like asking a champion sprinter to compete in a wheelchair race. He would be using totally different muscles, legs rather than arms, and get schooled by most everyone with a longer history. A champion bicycle rider would do better on this contraption than any champion swimmer.

(Due to water's density, champion speed swimming is also 80% technique and body shape rather than muscle/cardio. So until the technique is developed, nobody would be "good" with this thing.)

[iambateman]

TBH I think Michael Phelps would do just fine with this. :D