Go to the front of the wreck (Bow) there is a rope there, go near the rope.
Point your dive computer so they the Big S is right under the T of "FT"
Go straight for about 420feet....
Now can anyone tell me where to find that gorgeous sea turtle?
The turtle swims behind the ship, if you hover above the mission marker facing down the length of the yongala, you just go up and over to your left and that's roughly where the turtle should be =)