American swimmer Lynn Cox on Friday became the first person to swim across the cold Siberian waters of Lake Baikal, the world's deepest lake, the official Soviet Tass news agency said. Cox, of Los Alamitos, Calif., made the 11.1-mile crossing from Tolsty Cap to Listvyanka settlement in four hours and 20 minutes. The lake was at 51 degrees, Tass said. Cox, 31, was also the first person to swim across the frigid Bering Strait.