He's... he's not sinking, and that's all that matters in the end. Yuya's going to float behind Strange, giving him plenty of space to flail about without getting splashed. It's Koemi who pops up to swim beside Strange like some sort of constant demonstration, but given her short limbs and long body it... probably isn't very applicable to himself.

"You got it! Keep going, and try to move your arms and legs at the same speeds,"