I'm limited to pool training in a 25 yd shallow pool[4 ft deep]. Unable to find a club or training partner,so I'm solo. I swim for fitness 10X100 free on 1:40 breathing every 3rd stroke daily. I do O2 and CO2 tables after and under the watchfull eye of the life guard. She is briefed on what I'm doing. since starting I've been able to get to a 4:00 min breath hold. My goals are still rec freedives to 50 ft with 30 sec bottom time. Suggestions? I'm planning to take a course when one is closer to NC.