I was astonished at the dismal rating for this film, which at the time of this writing was 4.8. Into the Blue never demonstrated any pretense of becoming the next academy award winner, and instead faithfully executed its focus -- beautiful ocean scenery, beautiful bodies, and a significant degree of tension and action to carry the plot. I found the characters believable, especially given the target audience of the movie: the dialog was fairly cleverly humorous, but serious when it needed to be; the characters were adequately conceived, including the intentionally unlikeable 4th party woman who "wasn't family." Most of all, I enjoyed the pacing of the movie. Some slow underwater scenes were accompanied by peaceful music belying the increasingly perilous situations the characters found themselves in. Halfway through the movie, the tension never fully dissipates, as each event flows into the next as the stakes rise. The badguys are dealt with intelligently, and there are enough twists to convincingly carry the instability and danger of the situation.
I went into this movie wanting to enjoy it, and I wasn't disappointed. Though its premise wasn't the most intellectual of premises, I don't feel as if it were dumbed down as much as many action movies do, and instead carried out is plot with due respect given its expectations. I'd recommend this movie as a good post-summer adventure flick!