WAS TRAVELING 40MPH AT 9:30AM, ON A WET ROAD WITH LOW PROFILE TIRES WHEN VEHICLE SUDDENLY HYDROPLANED. SLAMMED ON BRAKES AND LOST TOTAL CONTROL OF VEHICLE. HIT A TELEPHONE POLE. CHILD SEAT DETACHED COMPLETELY FROM BASE ON PASSENGER'S SIDE AND ENDED UP ON DRIVER'S SIDE WITH CHILD STILL HARNESSED. CHILD SUFFERED A FRACTURED SKULL IN TWO PLACES AND WAS HOSPITALIZED. VEHICLE WAS 1986, NISSAN WITH NO AIR BAGS. *AK