Ianto can feel John's hand on his back and he supposes he trusts him not to just dunk him in the water for a laugh. He purses his lips and blows out a few breaths before leaning back into the water, maintaining his death grip on the other man's arm the whole time. The minute his shoulders and head touch he can feel his heart rate skyrocketing and he stands back up for a moment, his feet never really having left the bottom of the pool.

"Just... Just give me a second," he requests, feeling like an idiot because this really isn't difficult, it's just floating and John is right there. It's namely the fact that it's terrifying to give that control up to something that frankly scares him.

Breathing deeply and trying to center himself for another moment, Ianto moves to lean back against John's arm again, laying his head back in the water and reluctantly picking his feet up from the bottom in the attempt to do this right. John can probably feel his heart racing and his breathing coming a little too fast from where his hand is resting on his back, but by god he's making the attempt.