This quest is not available in game.
Recover the Sea Turtle Remains from the Skeletal Sea Turtle in the waters west of Auberdine, and then speak with Gwennyth Bly'Leggonde back in Auberdine.
That beached creature is not an isolated incident here in Darkshore. There are more along the coastline and even in the water. I would like for you to investigate another one that we know of; this one was reported to be in the water due west of Auberdine, close to a sunken vessel. Return to me with anything that you may recover that would aid our research.
Also, in your travels you may find other creatures. By all means, if you should discover anything then please bring it to our attention!