Take the Strangely Marked Box to Gwennyth Bly'Leggonde in Auberdine.
More sea turtle remains lie beached along the coastline. This particular set has an abandoned carriage attached to the turtle's shell. Perhaps this creature was driven to the shoreline by unknown beings rather than beaching itself as some of the other remains suggested. Greymist murlocs now make the remains of this creature their home, feasting off the carrion.
In the carriage, you find a box with strange markings on it; perhaps Gwennyth Bly'Leggonde in Auberdine can make sense of it.