Outcast Easter Egg - Hidden Sign

Go to the region of Okasankarr.
Go to the 'Darosham' - the building on the south side of the main island that has a flame burning inside.
Walk round the outside of the building and into the water. Stay close to the coast or the shark-creatures ill get you.
Swim round to the back wall of the building, and you will find a sign on the wall saying "No Public Urination"!