I have been whitewater kayaking with my pump on for a few months now without any problems. Tonight I went out with a fairly large group, and while we were gearing up to go out on the river, I keep my pump clipped to my board shorts. I do this so that I will remember to set my temp basal just prior to carrying my gear down to the water (this seems to work well timing wise, and tonight when I got out, my BG was 100, so my body seems to agree with this timeline too).
Anyway, this woman was getting set up next to me, and she looks over and says, "whoa, that looks pretty high tech - what is it? a cell phone or something? is it waterproof?...." and she just kept shooting questions at me before I had a chance to answer any - it reminded me of the scene in Home Alone when the neighbor kid is asking the airport van people a million questions. Anyway, I explained that it was an insulin pump, and that it was waterproof, and that was the end of the questioning. I was actually a little surprised when she didn't proceed with more questions about it - maybe she was taken off guard after being convinced it was some cool toy (which sometimes it is - I mean "normal" people don't get a pancreas with buttons and a cool screen).
The lady made me laugh a little and it opened up an opportunity for us to talk more, and we ended up paddling together for awhile. Happy to say I haven't had any issues with my pump or with my diabetes while out on the water. Any other kayakers out there??