If you are thinking fossil fuels or any other resource--the cost would still prohibit an active program of extraction.
Entire bands on the bottom of the ocean at mean depths are litterd with Manganese nodules (+ associated bunch of other minerals).
Several countries have looked into mining these areas--in fact cooperative efforts between the US, Japan, The former Soviet Union, Germany and a few other have occured in the past.
Still the potential windfall from these minerals is far less than the output cost to do it.