THE PILOT MADE SEVERAL LOW PASSES OVER A FROZEN LAKE AND BOUNCED THE GEAR ON THE SURFACE TO CHECK THE CONDITION OF THE ICE. HE THEN ELECTED TO LAND ON THE LAKE. DURING THE LAST 100 FEET OF THE LANDING ROLLOUT, THE MAIN LANDING GEAR TIRES BEGAN TO CUT A GROOVE IN THE ICE. THE AIRPLANE SUBSEQUENTLY SANK IN APPROXIMATELY 30 FEET OF WATER.