In search of new sources of oil, companies have been willing to go to greater extremes to procure it, including drilling beneath the ocean floor on rigs as far as 200 miles from shore and in water as deep as 7,500 feet. The first off-shore drilling began in the late 1940s and now takes place on platforms off the coasts of more than half the world’s nations. Drilling in such conditions is very dangerous work. Off-shore drilling, although more perilous and expensive, works similarly to on-shore drilling and produces the same negative by-products.