Aaron decided he was not going to miss out on the ability to get in a swim in a pool this fantastically warm. He took a running start and leaped into the pool, being immediately greeted by a warm, tingly feeling as his skin made contact with the pool water. He waded in place there for a moment, throwing his head back a little to breath; damn but it felt fantastic like this. Aaron let his head sink some more into the pool, enjoying himself, feeling up his body with his hand as he did so.
It was a long and arduous slog to get himself into this kind of shape, and honestly, Aaron was really happy it happened. Most people looked at him and they saw a nerd who probably sat at his computer all day. Shirt goes off? Opinions change. Just the thought of really enjoying the benefits of being one of the frankly best swimmers at the school made Aaron immediately think of the benefits to his dating life. Girls would not have looked at Aaron before, but now? He was getting interest, and if he could keep it going...
Aaron's fantasies, compounded by him idly feeling at his groin, were sufficient enough a distraction to lead his eyes away from what was happening to him. His hair thinned very slightly, turning from crew cut to more of a buzz cut on his head, while any vestiges of body hair fully erased themselves from him.
Evidently deciding to make this a time for his practice, Aaron went about swimming some laps, not even noticing when his best speeds and capability with this was going up steadily. He didn't notice his skin starting to change and get subtly rougher, tougher and more difficult to handle. Or that his teeth were sharpening, growing stronger and giving him a better bite. His body just felt so incredibly streamlined for the task at hand...!
He didn't notice that his rougher skin was forming a grooved, hooked look on a more intensive look that assisted in that, even as his ears slightly decreased in size. His body strengthened and for the time being his musculature inflated just a slight bit while preparing for what was to come later - more getting him into the right shape instead of changing him just into a more muscular physique for its own sake.
Aaron continued doing his laps even as it felt like his hands and feet were treading the water much more easily. While the webbing forming there was basic and not overtly obvious, it was enough of a change to produce a benefit to Aaron's swimming capability. His laps were getting faster and he needed fewer breath breaks, which he didn't even notice for the most part. He was getting to be more used to working in the water - and so while he would still be able to go on land, both the changes and the biological and chemical changes happening to Aaron would make doing so just a little more of a hassle.
Such that when Aaron thought he heard something darting around and the door to the old mansion slam shut and then open again, he stopped his laps and started walking toward the exit of the pool to investigate. He winced - the air outside was bitterly cold and just...for some reason felt bad on his skin. He groaned and shook his head a little, wondering whether to go and do what he was supposed to for this, or just head back into the pool...