If you see a white marker with an orange crossed diamond and black lettering in the ocean what does that mean?

A white marker with an orange crossed diamond and black lettering in the ocean indicates a "danger" area, meaning there may be hazards such as underwater rocks, wrecks, or other dangers to navigation. Boaters should exercise caution when approaching these markers and avoid the area if possible. The specific hazards may be indicated by additional information on the marker.