Shockingly, this turns out not to have been a movie interpretation of the classic Crosby, Stills, Nash, and Young album. However, there's a Beach Boys song.
Nevertheless, I hope readers appreciate the effort in getting those accents over the letters in the title correct; I don't have one of those fancy-schmancy HTML editors here.
Oh, yeah: the movie. Well, it's pretty good! Denzel Washington is our hero, an ATF agent investigating a horrific terrorist attack on a New Orleans ferry. But what starts out as a police procedural takes a science-fiction twist, … and I shant continue, because part of the fun here is figuring out what's going on, just as Denzel has to do.
The twist is contrived and ludicrous, but if you suspend disbelief just for that one little thing, the movie plays fair with you thereafter. It's not a spoiler to observe that Denzel develops a Laura-like obsession with one of the terror victims, and it's really kind of neat to see how that plays out.