One of the doors led to a cushy rodent pad complete with wood shavings, fresh produce and even Cheerios, while the other led to a shallow pool of water.
And the point is that the person who comes up with this thought experiment says that we are in a shallow pond thought experiment every day of our lives.
If temperatures get too high for the mangrove rivulus in the shallow tropical pools it inhabits, it'll flip itself onto a bank and cool off in the shade.