 hycom.Depth - HYCOM depth levels.
                 The data fields (specified in varlist) must be shaped
                 (x, y, z, time).
   start_date  = Gregorian start date array (YYYY, MM, DD, hh, mm, ss).
   varlist     = cell array of fields to use from the HYCOM struct.

 OUTPUT:
   Mobj.restart = struct whose field names are the variables which have
   been interpolated (e.g. Mobj.restart.temperature for HYCOM
   temperature).

 EXAMPLE USAGE
   interp_HYCOM2FVCOM(Mobj, hycom, [2006, 01, 01, 00, 0