Well, floating didn't look hard. It was probably something that got easier with a little practice, like anything else. Maybe actually getting into the water would kick start the memories that Roxas was pretty sure he should have, even if it's not remembering a specific instance. He's pretty sure it's not something he can rely on muscle memory for, just for the fact of what his situation is back home.

"Hm." He slipped into the water, noting that there was a vague sense that being in the water should be familiar. Well, he was in the shallow part of the pool where he wasn't actually in any trouble if he wound up sinking rather than floating. He could experiment.

A random thought in the back of his mind 'reminded' him that what he was experimenting with, what Sora was demonstrating, was sometimes also referred to as a dead man's float. Logically, that was because someone just floating like that might very well appear to be dead, but why did he know that random little factoid? With his thoughts elsewhere, even if it was a related tangent, Roxas wound up managing to float well enough without actually trying. Whether that would continue or not when he realized what he was doing remained to be seen.