THE PVT PLT HAD BEEN CLEARED FOR 27R ILS APCH AND WAS ON THE LOCALIZER AT 1,600 FT WHEN THE CONTROLLER NOTICED THE ACFT NORTH OF THE LOCALIZER COURSE AND IN A RIGHT TURN HEADED EAST. THE CONTROLLER QUERRIED THE PLT AS TO HIS HEADING AND THE PLT REPLIED, 'EAST, WHICH WAS TO GO?'. THE FLT WAS THEN GIVEN A TURN SO AS TO AVOID ANOTHER ACFT ON THE APCH WHICH THE ACCIDENT ACFT WAS APPROACHING HEAD-ON. THE PLT NEVER ACKNOWLEDGED ANY FURTHER RADIO TRANSMISSIONS AND SHORTLY THEREAFTER, THE ACFT DROPPED OFF RADAR AND CRASHED INTO THE ATLANTIC IN 800 FT OF WATER. THE NEWLY RATED MULTI-ENGINE PLT HAD BEEN ADVISED BY HIS CFI NOT TO CONDUCT ANY NIGHT IFR OR FLT INTO HEAVY IFR CONDITIONS UNTIL HE GAINED MORE IFR EXPERIENCE. THE WX CONDITIONS WERE NIGHT IFR WITH RAIN, HEAVY TURBULENCE AND THUNDERSTORMS IN THE AREA. NEITHER THE ACFT NOR OCCUPANTS WERE RECOVERED FROM THE OCEAN.