At waypoint one, you should perform an elaborate ceremony and proclaim yourself King of the Castle and that your glorious domain stretches as far as your eye can see. For best effect, although not really important at all, you should perform this ceremony at high tide.
During this ceremony, you should count all of the vertical battens and posts that make up the railing on this accessible side of the castle (the whole continuous section of railing from one end to the other).
Since the King of the Castle should have some treasure, you shall find yours a short distance away, using the instructions below.
Where X is the number of vertical timbers in the railing (battens and posts included):
Add (([the final 2 digits of X] - 2) / 3) to the final three digits of the South coordinates.
Subtract ((X - 60) / 2) from the final three digits of the East coordinates.
May your reign be prosperious and your royal cache finds plentiful, but please cover the treasure well when you leave so that the dynasty may continue unhindered for many generations of royalty!
All hail the King of the Castle!
Defiant980