The SC-HF GPS marking buoy is specifically designed to mark flotsam as used for tuna fishing. The buoy is moored to flotsam released at sea to mark shoals. The SC-HF GPS buoy is a sturdy half sphere made of moulded plastic (400 mm diameter). The standard model is equipped with an antenna 2.5 m high, an HF transmitter, a Global Positionning System, a flashlight and a temperature sensor. Buoy characteristics make it difficult to spot.