When I went on hols to Turkey last year I used SkinTac before putting it on. Went into a Turkish Bath, diving and swimming everyday and it stuck to me like a limpet
I cover mine with a square of lint and some Opsite Flexifix from a roll. I swim train regularly for an hour at a time, so put it on as soon as I put on my new Libre and I keep it on til I change sensor. I spray Cavilon underneath as I itch without and it helps to keep it on and prevents knocking off.