Before I started using a Libre poolside, I had a real problem with hypo awareness.
I passed out while swimming a few times in the pool. Needless to say, it is not a good day when you wake up in an ambulance being taken to the hospital. That horrible feeling of being partly unaware of what is going on around you, followed by the intense cold and shaky for hours is not pleasant.
Before I got the Libre and after I had a few bad episodes in the pool, I started getting out of the pool once, twice, or more during each swim to check my BG. That worked okay, but was a nuisance. Often someone would come along and take my lane (I always swim next to a guard and let all the pool/rec center staff know that I am a type 1, and what to look for) and it would be hard to keep in synch with my swim group.
The Libre allows me to scan as much as I want. I swim a lot of longer sets (eg 500 yards or more) and check between each set. I can watch the trends and get something to bring my BG up; of course calibrating for the fact that the Libre reading my be 20 or 30 mg/dl too high at that point in time. That is, if I get a scan that reads 120, I know that I may be 90 to 100 and need to get some glucose.
I cannot swim well if my BG is below 80 or 90. I can tell that I am not able to hold my body horizontal, get good catches, or adequately apply force on the water for propulsion.
To bring my BG up when needed, I keep an insulated bottle of cytomax at the poolside. It is an energy drink (powder mixed with water) that also replenishes various electrolytes and is fairly cheap. A couple of drinks from the bottle and a very short period of time will bring my BG back up.
With respect to the CO 10, I complained to my endo about the cramping due to the statins. He recommended the CO 10 and has worked well. I stall may occasionally get a cramp if I try to keep up with a college div 1 swimmer, but for most of time I am free of them.
Comfortable BG for swimming? As noted above, I can tell I am losing strength and reflexes when my BG is below 80 to 90. I have found that my better times are when I am between 120 and 150.