Did you see the "Behind the Scenes / Tell All" show? It was pretty interesting being "In the heads" of the "Survivors"; you had people who almost hated each others guts having to depend on each other for 21 days.
There was more medical intervention that was not shown in the series, I think it would have been impossible for the ones who made it the whole 21 days to have done so without medical support for the cuts and bruising; too much chance for infection. The fellow "Puma", who drank the un-purified water had to be airlifted out to a hospital for a weeks stay. He says, a year later and he is still not 100%.
Watching all of the episodes gave me a healthy respect for those teams that completes the challenge; suddenly, it seems like a good idea to stockpile a punch of drinking water and Bic lighters.
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