Barrel mark
A ton line is a series of the fairway characterizing tons . For example (coming from the sea) the red on the port side or the green on the starboard side of the fairway ( IALA region B vice versa).
The buoy line is the imaginary line connecting these lined up, floating sea marks. Driving over the buoy line can be dangerous , depending on the draft of the ship, as this would leave the fairway and reach shallow water areas. A watercraft outside the fairway is here outside the buoy line .
Driving within the buoy line is also important for the right of way , as these vehicles have priority on sea waterways as long as they are driving parallel to the fairway. This regulation does not apply on inland waterways .