Already played FFX-2 but this is what I thought when you see Tidus waking up in the water:

Remember before Yuna's speech? She was whistling by the OCEAN, of course to call for Tidus...
Well, Tidus wakes up in a body of water and I thought "oh crap, he somehow popped in the ocean (don't ask me how) and he heard Yuna's whistling."
That was my theory...until X-2 came out.

haha, I thought (if my theory was true)...how come he didn't get in the stadium to see her??? Well, they ran out of tickets to get in and then the Yevon monks recognized him and remembered he was the traitor of Yevon that got them all fired so they threw him in jail and he was officially screwed...lol, cruel but nonetheless, I thought it was pretty funny.