First, to prove or disprove a myth you need to simulate the conditions as near as you can-something which never happens on the show.
The myth about duct tape saving a man's life might be true, but not in the way they showed.
First, the presenters are on an island and are supplied with several miles of duct tape- who (!) carries that much in one trip?
I don't know about you, but the first thing I would do is make a huge fire, not spend hours doing SOS in duct tape, out in the blazing sun.
Next on my list would be an off the floor, simple and effective platform to rest on-this was the last thing they chose to do on day 1. When they were already de-hydrated and tired.
Another vital, yet ignored factor is the man on the island never knew if he would be rescued, whereas the presenters knew there was a film crew and at any time they could call the idea to a halt. Desperation leads to a mental health problem.
What amazes me, after 2 days neither man has designed a toilet or even dug a hole to be used-I guess the portacabin off the set is fine for that.
MYTH busted LOL