How on earth do you do the walk around ?
The short answer is "very carefully"
The longer answer is that the best way is before you launch the aircraft, while it is still on dry land. However, you will need a tall step ladder to check the ailerons.
If it is already in the water at a dock and you REALLY need to check the other wing, you can untie the aircraft and carefully swing it around to check the other wing and the tail. This should only be done in relatively calm conditions and most importantly - don't let go!
Most pilots work on the principle that "it was OK last time."