I could understand this being 'predicament bondage' if the shared chain was long enough for only one of them to reach the surface, but the depth sign behind them reads '10m', not '3m.'

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thescarredman said:

I could understand this being 'predicament bondage' if the shared chain was long enough for only one of them to reach the surface, but the depth sign behind them reads '10m', not '3m.'

As in what is implied by the 10m written on the wall. But we do not know how much of the pool is actually filled with water.

It's a predicament because of the key that's been dropped into the pool between them. Artist says it'll unlock either of their collars, but locks in place once used and thus can only be used once, and the collars too big to fit through the loop on the bottom. They were presumably told all of this before being sunk.
One lives, one dies. Fight!