Yes I rented it. Yes we watched it. You know what it was actually perfectly reasonable. In all honesty I'll buy it if I see it on sale somewhere. Why?
The movie chugs along, blah, blah, blah, beautiful beach people, beautiful beaches and then BAM! actiony goodness. The movie goes sideways in the third act and turns into a kick ass actioner. There are several brutal shark attacks, shootings, spearguns, Jessica Alba whomps the shit out a dude, another brutal shark attack, and a couple of painful impact shots.
We really weren't expecting to like this movie at all and really it wasn't very good but for a summertime popcorn movie it hit the spot. The acting is respectable, the story is a knock-off of Benchley's The Deep, the chicks are hot, the dudes are buff, Scott Caan is probably sick of hearing that he really looks like his Dad, and there are sharks and people in SCUBA gear fighting. I'm a sucker for movies with sharks and people fighting in SCUBA gear in them. Thunderball is my favorite Bond movie for this reason.
Don't scoff, get off your high horse, and just rent Into the Blue. It's good summertime fun.