If you swim for long periods, run, or do contact sports, you may need to give your sensor a little extra help in staying stuck to your skin.
RockTape kinesiology tape
If you need a larger patch with more grip and stretch.
Nonadhesive wraps
Non-adhesive wraps work by gently clinging to themselves without sticking to the skin, providing secure support or coverage without the need for glue or adhesive.
Underwrap - you can put this under adhesive tape
Iv3000 dressing - Smith & Nephew
If you have trouble with standard patches or kinesiology tape, this is a good alternative.
Hypafix - hypoallergenic dressing tape
A self adhesive, non-woven tape usually used for dressings. Apparently this is good even when wet.