DENVER — A search resumed Sunday for a man missing after flipping off his inner tube in rapids on the South Platte River. Sheridan police were called to the river around 4:30 p.m. Saturday. Witnesses say the 20-year-old surfaced and went under several times. Rescue crews combed the banks of the river and stopped looking for him at dark before resuming the search on Sunday. The man was one of four tubers.