If a person has a C1D visa can he enter US as a visitor?

The C-1D visa is a non-immigrant visa class specifically for the use of ship or airline crew who are non US passport holders or permanent residents and allows them entry to and exit from the United States.

The C-1D visa is for crew members who intend to arrive in and exit from the United States with the same airline or on the same vessel.

http://www.visabureau.com/america/c-1d-crewmember-visa.aspx