i WEAR the dexcom seven. have a pool- no problems with up to one hour of swimming. but I am an adult.
I'd guess some tegraderm or tape would be added insurance.
used to wear the minimed sensor. the dex com tape is WAY WAY stronger.
An update: we switched to Dexcom 7+ and love it! The adhesive is much stronger, and lasts most of the 7 days. I put some tape on it when it's getting iffy.