I sent the image off to a friend at SP HQ and had it enhanced using the latest crime scene photo analysis techniques. The yellowish hue was due to excess tannins in the water, but after a little filtering this is what the picture revealed:
Attachment 682
Rumor has it that a suspect in a well worn aluminum boat coated in rustoleum paint was observed trying to attach the sign to a nearby piling, but it fell off shortly thereafter. Authorities are trying to track the suspect down using a Walmart receipt found near the scene...