I have not heard a satisfactory practical reason why someone would want to wear boardies over a wetsuit. There's much better ways of storing keys and carrying cameras.
Personally I can't understand why you would want to have an extra thing that you have to take to the beach and gets wet and has to be dried and all that. It offends my sense of aesthetics in terms of form follows function.
Robbie Naish says he wears boardies over a wetsuit because it makes for nicer photographs. I guess they add a bit more colour and another spot for a company product and logo to be featured (especially if your company doesn't make wetsuits).
Boardies have no function over a wettie so they look wrong, especially in kiteboarding where they ride up and create the chicken-leg look. I guess that makes a case for the alternative, wearing a wetsuit under boardies to avoid the bad look of having the legs of the boardies wedged up around your crotch. (
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