Reminiscent of Laura with beautiful Gene Tierney and Dana Andrews 1944 where he falls in love with the portrait of Laura while investigating her death...and I agree that the alligator would have finished with the body before Denzel showed up...
I liked this movie. Even though it's one of the most unrealistic plots the writers could muster up. If you can get past the MANY MANY things that would never make sense, it can be enjoyable.
I remember seeing this in theatres in Dallas, TX and I really enjoyed the NOLA aesthetic it portrayed in the movie, then I moved to Kenner, LA for a nice pest control job and the area I often do pest control service in is the Algiers and surrounding areas. It's got some lovely parts and some that are not so lovely, but I've never seen a place with worse road infrastructure than NOLA and I didn't see roadwork signs, construction cones and tape and entire neighborhoods blocked because road construction could in theory be happening, but I've never seen any road workers in those areas fixing roads. There are better roadways in 3rd and 4th world countries when compared to the roads in NOLA...
There is a continuity issue with the timeline. The ending doesn't work and only does so because of deus ex machina. We see that he has already tried when we get a remembrance of the bloody towels in the beginning of the film when he visits the girls house. This tells us that he has already tried saving her and gave all the clues early on. But when watching the film, the boat explodes, so he is in a loop where he ends up dying in trying to prevent the ship from exploding.