Ansys Employee
Without operating density input Solver will automatically parse it with data from the case and that data might be wrong depending on flow/material properties.
If you put it now to zero then you need to adjust all openings pressure: pressure inlet and outlets as they now require Absolute Pressure Input taking into account the hydro-static pressure.
It is not wrong to use steady if the flow is steady and no transient effects need to be tracked. IF you are doing a multiphase run for your submarine then probably you require unsteady solver