Bike Forums - Heart Rate Monitor Leak?

Do any of you have problems with heart rate monitors allowing water to get into the wrist-watch unit? I've had 3 units do this to me over the last 1.5 years, and the last 2 were within the last couple of months. Is this common? I'm tired of buying new ones!

Could it be my sunscreen eating away at the gaskets? I thought that you were supposed to be able to swim in these things, but mine leak in rainy conditions on my bicycle. Should I not buy a wrist-watch type of monitor next time, or always hook it up to the handlebars when I use it? Thanks.