Somewhere between zero and what Warrior said.
The coverage appeals to pedophiles, people who like going for a ride on a bike and the usual suspects who follow tennis or soccer. Swimming appeals to people who miss Oprah and track and field might be watchable if there is nothing else to do. The main problem, in the US, is that it's about one hour of action spread over six hours of coverage that includes the usual overcoming adversity stories, chronic talking heads and commericals for McDonalds and NBC's lame fall line-up of new shows. Everyone has a sob story as they are paid by the government to exercise.