Haven't looked at the other threads on "Open Water" but then it doesn't matter does it? You asked for peoples' opinion didn't you?
I thought this was a well done film in the same genre as Blair Witch Project. In other words it used the Home Video Method to add to the realism, suspense and horror. If the film had used slick special effects and artsy filming it wouldn't have been nearly as effective in flat scaring the pants off the audience.
The theatre I saw the film in was about 1/3 full. Periodically throughout the show there were audible gasps when there was an especially scarey or startling scene.
While I'll not give it away, the scene next to the ending was simultaneously extremely sad and horrifying.
In short, if you are a fan of horror movies you will like this one. But be warned that some of the scenes will stay with you for awhile. I can still see the last scene with the divers.
That all said, like any piece of art, there will be people who will like the movie and those who don't. You pays your money, takes your chances and makes up your own mind.
Will the movie stop me from diving? No, emphatically no! Anyone who would let this movie stop them from diving has in my opinion such a fragile barrier between fact and fantasy, real risk and imagined risk, that they probably shouldn't be diving anyway.
