What do diamond markers warn boaters about?

Diamond markers are specifically designed to warn boaters about hazards and obstructions that may pose a danger to navigation. These markers provide crucial information about underwater hazards such as rocks, shoals, or other obstacles that could potentially damage vessels or cause accidents. By being vigilant and paying attention to these diamond-shaped warnings, boaters can take necessary precautions, alter their course, and ensure a safer experience on the water. This proactive approach is essential for maintaining safety while navigating through potentially dangerous areas. The other options focus on different aspects of boating safety and regulation, but diamond markers specifically serve the purpose of alerting to hazards in the waterway.