It's a fantasy role-playing game.

DM: You are Vax Vax'ildan, a half-elf rogue . You are the member of the famous group of adventurers. Previously, She rents them a boat called the Shore Shanty, helmed by Captain Santy, for three days' use. After about two hours of sailing, they arrive above the undersea volcano.
DM: You watch as Vax disappears into the liquid. The pressure is a lot. I need you to make an athletics check first.
Player: Okay, that's what I'm best at. Athletics. Natural 20. Thanks, Matt Colville.
DM: You swim down into the darkness and you're using your sense of balance to keep tabs on what is up and what is down, because once you dive into the middle of this pillar you see nothing. And you begin to swim down, feeling for where the gravity is pulling you and the force against you, and use that to get your bearings.
Player: I know it's probably fuck-all, but I'm going to pull out the Flametongue Dagger and try to use it as a shitty-ass--
DM: You can faintly see a little bit of it there. You do take three points of fire damage as soon as you enter the water, reduced to one. So you manage to push through and descend about 15 or so, 20 feet. You suffer another six points of fire damage, reduced to three. Need you to make another athletics check, please, as you're pushing further and further down.
Player: Use my first Luck of the day. Oh, not good. Same thing. Just a six.
DM: A six? It begins to push you up, you lose a little bit of ground. You take another one point of fire damage. You begin to make up, and you get partway down. You get another 40 or so feet down into it, you think. Still unable to really see anything. Occasionally, you see a glint of that light that you saw before. The little bit of glow. You take another three points of fire damage, reduced to one. It is a lot of heat, but you continue to push further. Make another athletics check, a third one.
Player: 20, total.
DM: 20? (grunting) Pushing along, still making your way down, making your way down. You get probably another 80 or so feet before it seems to curve off a little bit to the side. The force of the water begins to shift a little bit. You take another three points of fire damage. You begin to see a faint bit of that glow that you were following earlier, and as you head towards it the heat gets more and more intense. You begin to push past some of the smoke, and you can see right there, looks like there's a glowing ember of rock about five or six feet wide that is molten rock that is slowly cooling as it's being pushed faintly out, but the force of the water curves off to the side and you continue to swim away from where that glowing ember is and following the path of where this push of water is. You take another two points of fire damage.
Player: Okay. I'm Ed Harris, sinking down and down and down.
DM: The temperature is going up. You continue to swim, continue to swim. Further down, further down, further down. Make another athletics check.
Player: 16.
DM: Okay. You're slowing down a bit, but you're still getting ground. You also take another three points of fire damage. This is getting hard.
Player: Yeah?
DM: And even your form, you're getting a little tired, having to go against this force. And you're not quite sure where this is going to lead you. You're not going to stumble across an opening where it's fine to walk. You're continuing to swim down a superheated--
Player: I'm going to push it just a little bit more.
DM: Okay, make another athletics check.
Player: Okay. That's not good. That's a seven.
DM: Okay. You get pushed back about 15 feet or so, and you take another three points of fire damage.
Player: And I'll go with it, up.
DM: Okay. You ride up. Before you can get entirely out of the column, you take another three points of fire damage and eventually emerge from the side of it. Uncomfortable.
Player: Back into warm piss water, instead of boiling hot.
DM: Yes, which comparatively is much more comfortable.
