What is an indication that a vessel is operating in a keep-out area?

A vessel operating in a keep-out area is indicated by an orange crossed diamond marker. This specific sign serves to alert boaters that they must not enter the area, often due to safety concerns like hazardous conditions, wildlife protection, or other regulated zones. The bold visual design of the orange crossed diamond makes it easily recognizable, helping to ensure that boaters maintain a safe distance from potentially dangerous or restricted areas.

In contrast, other markers do not convey the same restriction. A blue marker could be used to denote various navigational aids, a red buoy typically indicates safe channels or areas where boats may travel, and a yellow flag generally signals caution but does not necessarily denote a keep-out zone. Therefore, the orange crossed diamond marker is the specific and universally recognized symbol for keeping out of certain designated areas.