I use the Libre 2 sensor and swim 5x a week for c.50 mins at a time. I was concerned about getting the sensor wet etc too, though the blurb says it’s ok for 30 minutes but I have found it ok for much longer. I did buy a Libre arm band that goes over the sensor, though oddly has drops of water inside when you take it off, so not exactly waterproof…but occasionally with some placements on the arm it used to rub uncomfortably against my lower armpit/ breast side, so for those two weeks didn’t wear it. I have had some sensors failing, largely the filament bends, but the adhesive is still completely sealed on the arm…Abbott happily replace failures ( and it’s easier to log in complaints about failure online instead of phoning). I don’t have the patience to use various plasters people have recommended previously, nor the purse to use them 5+ times a week!