Double-hulled tanker

A double-hulled tanker is a large tanker ship used for transporting liquids (usually petroleum).

The ship has two hulls to prevent the liquid cargo from spilling; if the outer hull is breached, the inner hull keeps the transported substance in place.

Double-hulled tankers were required after the Exxon Valdez oil spill. The United States Congress passed The Oil Pollution Act of 1990[?] requiring double-hull tankers now, but allowing the transportation companies until 2015 to replace existing tankers.