The ground disappears from beneath your feet

And you're falling. You briefly hit stone with your feet which sends you spinning in the air and causes you to scream out in pain. You fall for another second, lose grip of Russ's body and then you hit water, vertically, luckily for you. The first sensation you get is the bone-chilling cold of a subterranean lake. Then the water in your mouth and your lungs. The third sensation is something you hadn't registered before. As you swim your way to the surface, your motion causes bioluminescent particles in the water to emit a faint blue-green light. Your eyes, now adjusted to the darkness, drink in this faint bit of luminescence the way a thirsty man drinks a swig of water. It is divine.

You take a moment to take in the sight around you. The water around you stretches out into the darkness beyond your sight, but above you the ceiling of the cave is quite low, judging by the bioluminescent plants that hang from the ceiling. Everything here seems to respond to the slightest movement, so the ripples your current splashing is making in the water sends waves of light across the cavern and slowly all of it lights up.

Doing the only thing you can do, you start to swim, forgetting all about Russ' corpse, you just try to find a place, any place, where you can make land and rest. After a short while you see the rock of the cave slope up and turns into a rocky beach. However before you reach it, you feel something stir in the water beneath you.