I think this may be "Greenface" by James Schmitz. I found it in the anthology "Agent of Vega", which is scifi rather than horror, but it may have been anthologized elsewhere. The story can be read at the first link.
The story is indeed set in a lodge, in a fishing camp, with a lake and woods and weedy patches. One protagonist, Hogan Masters, is the boss and owner.
The titular character, Greenface, is indeed a small, greenish creature with a face like a smile
It was a shiny, dark-green lump, the size and shape of a goose egg standing on end among the weeds; it was pulsing regularly like a human heart; and across it ran a network of thin, dark lines that seemed to form two tightly shut eyes and a closed, faintly smiling mouth.
It is also later described as a mass of jelly
There was nothing very solid about it, you know. Just a big poisonous mass of jelly from the tropics.
so jellyfish would seem a good description.
There are several references to it as ghost-like, for its ability to appear and disappear and the ribbons of its body seeming cloth-like and shining. The aforementioned ribbons by which it moves also seems to support the "jellyfish-like" descriptor.
It appears and disappears throughout the story, scaring the protagonists, something like a ghost-like haunting. It also gets bigger and bigger as the story progresses - at one point is more than thirty feet big. I believe it did have an ability with appearing and disappearing, not sure if it was invisibility or teleportation or something like that. It does, in fact, feed on animals (starting with a snake), and hunts humans.
It also stopped moving when in complete darkness, some kind of paralysis, though even a sliver of light would let it move (as in moonlight or starlight) - the main character thinks to trap it that way at one point, and is thwarted by such a natural light.
They also do eventually kill it by trapping it in the lodge basement and burning the lodge down.
