Your 240-feet underwater, floating in darkness by the entrance to a deep cave, before it

stands a sign with large block letters and a simple warning, stop, prevent your death,

go no further.

Though eerie, you're an experienced individual, with a license as an advanced open-water

diver, with several trips within caves, you proceed, ready to map out thus far on explored

regions, only a tri-mixed tank and a mouthpiece keeping you from an unpleasant demise.

Proceeding within, you are shocked by the overwhelming darkness.

You turn on your flashlight, which gives you a good view of the clear waters, but it also

creates a bizarre sense of being trapped within the narrow passages.

The plan has been attached by the entrance, serving as a passive guide into the network

before you.

The plan is to extend deeper into the network of caves, but should you lose it, there

is no calling for help, no turning back, no hope.

You'll get trapped, panic, and inevitably drown.

Despite this, you keep moving, deeper and deeper into the darkness.

You eventually reach the end of the marked path, not even noticing the slight decline

leading even further into the depths of the ocean.

After 30 minutes in the cave, you check your residual pressure gauge, estimating the time

you have left before surfacing becomes an absolute necessity.

Within your tri-mixed tank and a reserve, you have just over two hours underwater.

One third was reserved for the journey downwards into the cave, which happened so far without

incident, leaving a generous margin of error.

...