Offshore drilling typically refers to the discovery and development of oil and gas resources which lie underwater. Most commonly, the term is used to describe oil extraction off the coasts of continents, though the term can also apply to drilling in lakes and inland seas. Offshore drilling presents environmental challenges, especially in the Arctic or close to the shore. Controversies include the ongoing US offshore drilling debate. The off shore moratorium in the US (as a result of the BP spill) ended in October 2010. The Obama administration has decided to allow 13 companies to resume deepwater drilling without additional environmental scrutiny. The decision comes after the administration said it would require strict reviews for new drilling in the Gulf. Others, such as the arctic Shell project, are still blocked by related concerns. The Department of the Interior apparently gave those companies the go-ahead because they were in the middle of previously approved projects when the Gulf spill occurred.