Question about Harper's escape plan (SPOILERS)

Harper's plan to get himself and that woman (played by Gayle Strickland) out of the room they were trapped in proved in the end to be pretty stupid, right? His plan called for flooding the room with thousands of gallons of water so they would end up floating 25 feet to the ceiling, thus allowing them to reach the skylight, break the glass, and pull themselves up through it to freedom.

Am I right so far?

But when the water finally rose to ceiling-level, they realized to their horror that they COULDN'T BREAK THE GLASS!

They were just about to drown in Harper's home-made fish bowl -- and surely would have, if someone hadn't yanked open a door at the very last second.

My point, of course, is that Harper's plan was not only half-baked, it nearly got them killed.

Is this description accurate, or did I miss something here?