A much more somber and thoughtful piece then I was expecting, and certainly memorable. I'm not sure it's a place most typical greedy/ goal driven PC's would be satisfied with finally finding. (given there's no treasure or other tangible rewards to be gained from the place and no great "villain" to overcome.)
Nonetheless, for those looking for a memorable legend, and a equally memorable location, they would be hard pressed to find one more so.
A bit more detail about the rumor of "You will not live to see the New Moon after witnessing its beauty." might be a worthy enhancement. I can feel there is potential for a surprising climax here with the PC's being attacked by whales, or some type of water elemental near the beginning of the new moon, seeking to return them to the watery grave as well.