I like the line "Not enough full moons, not enough setting suns" It represents time and two of the most pleasurable things in life. If you haven't seen either, then you haven't lived. So it's that they have not lived long, plus that they have not experienced it. I like poems with new ideas, the stream is a new way of describing the afterlife, and you don't use too many metaphors that makes the poem hard to understand. If I were you I would only make it clear that you were talking of death in one line(near the middle or at the end), and the rest of the poem would be talking of a stream and a friend. I encourage you to write many more with this theme of the stream, then choose your favorite. It's just too good of an idea to waste on one poem that may not be your best work.