Hapi was the only God of the Nile. He was also called the "Lord of the fishes and the birds". I think the confusion comes from the fact that there is another God who wears the same name: Hapy, one of the son of Horus.
Due to his fertile nature he was often considered as being the "Father of the Gods". He was a positive deity, drawn as a man woth a belly and a blue or green skin representing the Nun waters.
I hope it clarifies things for you.
I found Ancient Egypt fascinating by the way.