"Suuure, suure." Inigo is the toddler and Tidus must reassure him that the water isn't going to swallow him whole if he's under it for five seconds. It's amazing what can get Inigo wound up, but Tidus figures it's genuine - this is just Inigo, and all they can expect from him is for him to do his best.

And it's only for Inigo that he offers, as he reminds Inigo:

"Remember, count to five, in your head. You don't need to open your mouth. And if you really want..." Out comes his hand. "...You can hold my hand while you're doing it."

A beat. "Just don't yank me under too."

He knows what you're like, dude.