Freestyle Libre

I believe @kev-w uses tegaderm and he's a swimmer, can't speak for it or anything similar myself though as I'm not a swimmer.

I do indeed, in the UK I buy it from Boots chemist, it's ok but 6 swims and it'll peel, I've learned to keep pressure on he sensor while I remove it and put a new piece on.

I've seen Opsite flexfix mentioned too.

Edit, the sensor is waterproof, 'they' say for 30 mins but I've managed around 45 before with no issues, I hedge my bets and swim shorter times the first week and longer for the second.