What symbol on regulatory marker is used to warn of underwater hazard?

Diamond- Non-lateral markers are navigation aids that give information other than the edges of safe water areas. The most common are regulatory markers that are white and use orange markings and black lettering. Danger area markers (with diamonds) warn of dangers such as rocks, shoals, construction, dams, or stumps. Always proceed with caution and keep a safe distance. Never assume that every hazard will be marked by a buoy.