At 1205 Pacific time, a Cessna 172M was ditched into the ocean near Torrance, but the pilot was uninjured. The pilot said he was flying from Apple Valley to Catalina Island at 8,500 feet when he descended to avoid the Class B airspace at Los Angeles. He leveled at 2,500 feet and noticed an unusual vibration in the cowling. He reduced power but mistakenly applied carb heat, which he could then not remove. The EGT showed the airplane running hot, and he realized he had not enriched the mixture since descending. However, the mixture control also was inoperative. He turned back toward shore and deployed full flaps to descend to the water.