Mystery Bird?

This fine-looking bird was sitting along side the path through the mangroves behind our cabana that leads to Black Creek.  It let me approach quite close before it flew into the mangrove roots.

By size, shape, neck length, and habitat, it keys out to be a green heron.  But it is the wrong color and has a darker beak than green herons usually have.  After much searching, the most likely ID is a dark form of green, striated, or green-backed heron.  Some sources lump all those 3 into one species, Butorides striatus.  I hope to see and photograph this individual again during different seasons.  Any insights into the ID will be greatly appreciated!