Some fish, like sharks, don’t posses an air bladder to help keep them afloat and must either swim continually or rest on the bottom.  

U.S. Department of the Interior

March 25, 2011 | Categories: Resources

The U.S. Department of the Interior is a Cabinet-level agency that manages America’s vast natural and cultural resources. Secretary of Interior Ken Salazar heads our department, which employs 70,000 people, including expert scientists and resource-management professionals in eight technical bureaus.