Shipping accidents are a pressing concern, as several commercial shipping routes pass through the Great Barrier Reef. Although the route through the Great Barrier Reef is not easy, reef pilots consider it safer than outside the reef in the event of mechanical failure, since a ship can sit safely while being repaired. There have been over 1,600 known shipwrecks in the Great Barrier Reef region. On 3 April 2010, bulk coal carrier Shen Neng 1 ran aground on Douglas Shoals, spilling up to four tones of oil into the water and causing extensive damage to the reef.