I think I've decided against my initial sketches, will make something more along the lines of a tree symbiote or parasite, something that latches to a tree specifically and uses it's tongue to snare prey that way.
Well draw later, I'm very tired
As for others sketches,
Loving sketch 1 myself, can imagine it in a really twisted landscape, not sure how 1 and 3 need to be prehensile though, especially if it's for gripping fish, the spike seems very useful but there's no real need for a prehensile ability.
I personally love 2 and 3, mostly 3 because of it's silhouette, I think 2 would make more use of a prehensile tongue though. Looking forward to seeing which you choose and how it develops though.