@emfor How are you trying to get your Libre scanner to read? My ocean water isn't cold so I haven't run into that problem. I do know that bluetooth communication doesn't work underwater. But so far with the 14day Libre and the Libre2 and the reader in a waterproof Stash pouch held right over my sensor has given me a scan? (the phone does not work) I also keep the reader shoved between me and my swimsuit so it probably helps keep it warmer. The Stash pouch has never failed, I have 3 of them, one for my phone, one for the Libre reader and one for a bag of ginger candy.
Before getting my Libre to scan I used to limit my swims to about 1 hour because that seemed to the safe time period, although a few times I came out at around a 4.1. In my case with a pump I reduce my basal rate for 2 hours prior to swimming. I have an Omnipod so I reduce and don't completely stop it. The additional option is to boost your BG level more before you swim. I used to boost it to around 8.3 before. Now I just boost it to around 7.2. I make sure I don't eat in the am so that I had no bolus insulin on board when I swim and in my case would drink some chocolate soymilk to boost it up to the level I want before I swim with no insulin. Having any active bolus insulin makes it a lot harder to stop having hypo's.
I ran into that the other day, we spontaneously decided to swim and I had eaten and dosed for a larger carb lunch. I ate some extra peanuts and caramel to boost me more and went in to promptly fall 4 mmols in only about 4,000 feet of swimming. I downed a few ***** bears, swam to shore and promptly downed half the bag and then went back out. And you can't always tell what exertion you are going to expend when swimming in the ocean so that adds difficulty.
But maybe try to work with the Libre more? Insulate it or???? Because I used to always worry what BG level I was at and it influenced how much I enjoyed it and how far and long I swam. Now I just check my Libre and that allowed me to learn what to do to stay out longer.