this is why I'm on the Animas - only waterproof pump on the market.
Medtronic buttons would get "stuck" even by sweating on it a little - so frustrating!
I tried everything too - from covering it in plastic, to sticking it in a ziploc, etc.
It's worth noting that maybe you could give yourself a bolus for an hour or two in advance and then just take the thing off for a couple of hours at a time?
That's what I'd do when I ran since I'd usually suspend it anyway since I go low when I run for over 45-60mins.
Now I just wear my Animas and sweat all over the thing... I've even worn it during snorkeling in Thailand and that was cool