If you take the Hippogryph flight from Moonglade to Rut'theran Village, you will actually fly RIGHT over the "V"-shaped rocks! So, if you want a quick preview as to where you will need to swim, take this flight and flip on your map, when you see the rocks, for a precise location. You can even see all of the threshers from the flight, just make sure to look down at the sea!

I hope this helps anyone else who is trying to do this without coordinate addons.