Absence seizures, swimming, exercise, and independence

I'm wondering about, well, a lot since my 12-year-old was diagnosed with juvenile absence epilepsy a couple of days ago. But today, two items have been on my mind. First is swimming. The neurologist said he can absolutely swim, but always with an adult present (which we've always required anyway). My extra concern here is that I'm not sure it would be easy to tell if he was having an absence seizure while swimming. We've never observed one while he's physically active. Only while he was sitting and engaged in a conversation, like during dinner or going over homework with us. In truth, we've observed very few absence seizures over the past maybe 3-4 months (only recently did it even strike us as an issue, as we first thought he was distracted). Of course, we know there might have been episodes we haven't seen. The fact is, if he had one and we weren't talking with him, it would be darned hard to notice anything at all. And that's what worries me. If he's swimming underwater, or if suddenly goes underwater (while playing in the pool), it might be extremely difficult to know if anything is wrong, even if he's being carefully observed. The neuro said that it's actually very unlikely that he would be in danger if he had a brief absence seizure while swimming (I'm not sure why, and we were so overwhelmed during the meeting that I didn't ask him to elaborate), although of course he said he needs to be monitored in a pool. I'm quite confused here. Next, exercise. During the 1-hour EEG, he only showed seizure activity during the hyperventilation portion, and a very brief episode almost immediately afterwards. That was later in the EEG, almost near the end. My son does a lot of physical activity. Tennis, karate, skiing and a sort of junior level crossfit program. Sometimes in the conditioning part of crossfit or during the exercise portions of class in karate, he does get extremely winded. Is that something that could trigger a seizure, given the hyperventilation results on his EEG? Finally, he's almost 13 years old. Yes, we do leave him home alone at times. Nothing crazy long, but maybe a couple of hours. Certainly we don't drag him out for errands, or things like that. Is that OK to do with absence seizures? His observed seizures have always been at absolute most, 10 seconds, and my husband and I are quite convinced they were more likely 5 seconds to be honest. None of his friends or teachers have noticed any. His Hebrew school cantor did see an episode a bit over a week ago, but that's it. Also, I'm terrified about what would happen if he had a tonic clonic seizure while we're gone. I know this could potentially happen someday, especially with the juvenile form of this. The medication he is on is Zarontin, which only controls absence seizures. Any thoughts or experiences would be greatly appreciated.