Just had my swim this morning. Swim 70 lengths and am in 45 minutes 3 times a week. I make sure I’m not too high/low when I go in, have jelly babies at the side of the pool and don’t worry about phone. It is in a bag with all my other diabetes stuff on the shelves at the end. It is often screaming at me when I get out to say levels are going above my 10 upper limit. I long ago switched signal loss alarm off. It drove me mad and I hate thinking it is controlling me.
I swim before breakfast, usually have a small amount of insulin as I always rise in the morning and the exercise shoots my levels up.
Experiment and see what works for you.
Get in and enjoy, it will do you good.