There's an Egyptian temple initiation that's similar. Down the steps into the water, swim under the wall. If you surface too soon you'll be met by alligators. You have to dive to the bottom of the chamber in darkness to find the exit and pass the initiation.
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Nightmarish, Courageous, Inspiring at the same time!

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For someone with claustrophobia, it's hard to even read
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I get claustrophobic enough as it is. Shudder.
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