Trailer doesn't offer up much and why does it feel like they turned Swamp into a villain? Also the look is not good to me and far too much CGI
I imagine that most of the trailer is from the first half of the film, when the creature is first discovered and is terrifying. My guess is that they're going for the classic King Kong plot, where, in the latter half of the film, the creature will show some humanity and bond with a human, generating sympathy from the audience, and the real villains of the story will be the "bad" humans who try to kill him. You may get your swamp superhero in followup films, but I think that it makes sense for him to not be that in the origin story.
I don't really agree about there being "too much CGI." We'll have to see, but it seemed like most of it was in one scene. It certainly appears to be much less CGI heavy than your typical comic book movie. At the very least, the actual swamp thing looks like a guy in a costume, which is awfully refreshing and a very wise choice, since making him CGI would've definitely been going too far, IMO.