In this paper, an investigation of unsteady free convective magneto-hydro dynamic (MHD) flow of salty water in the presence of a transverse magnetic field has been carried out. An electrically conducting and incompressible fluid is assumed to flow past a semi-infinite vertical porous plate. A constant magnetic field is applied normally to the vertical plate. The Prandtl numbers for salt water are taken to be 1 at 20˚C. The governing equations of the problem contain non-linear partial differential equations that are transformed into ordinary differential equations. An explicit finite difference scheme has been used to solve the transformed ordinary equations generated from this flow problem. The velocity profiles and temperature distribution of the flow field have been discussed and presented graphically.