Buoy is designed and built to enable sinking or floating to the surface.
A typical navigation buoy is a floating vessel that must be tended to each year prior to the point in time where ice could damage it. The time and expense needed to place and remove the buoy from its mooring is significant. To minimize the service cost, enabling the buoy to be submerged by flooding ballast tanks or allowing the vessel to rise to the surface using compressed air to blow the ballast tank could reduce the cost of upkeep.
Problem this idea/invention addresses:
In cold climates, where ice typically forms, navigation buoys are removed from service by plucking them from the water. To enable the buoy to dive or surface, like a submarine, means the buoy can be stored under the ice and away from damage.