I suspect that you will get mostly negative responses from the members here. I wouldn't do it, but like many other members, I have an SUV driven by the wife that can handle it. It would definitely "violate" the sports performance purity of the six and be a questionable move. I suggest you find a beat up pickup truck for less than a grand, which would do the job much better. One practical question might be the pull out of the water on a wet ramp, depending on how steep - I know a jet ski doesn't weigh much, but with that torque, the tires break free rather easily.... (I do recall backing down a snow-covered hill that my six couldn't handle in the last snow event here in Buckhead...
'07 650i vert, beige/jet black, sports & cold weather pkgs, comfort access, logic 7, sat radio, Miro M6 wheels (with Michelin super sports), M6 spare tire, tint, windscreen, triple resonator delete, m-tec v3 AE's bulbs, corner bulb delete and m-tec fogs
'11 Acura MDX Advance with Entertainment pkg for wife - no mod's
'04 Acura TSX (daughter) and '12 VW GTI - Autobahn (son)