DM Help, I don't understand the layout of the Smugglers' Tunnels under the Lucky Bones (Spoilers)

[Brenden Falke]

So, my players will soon enter the submerged tunnels, the lowest level under the lucky bones.

But I just don't understand the layout of these tunnels, specifically how they are laid out so an active pumping room can keep those tunnels dry.

Based on the descriptions, I can make out that area D9 eventually leads up to an area that's higher than the tunnels. D1, D2, D5, D6, D7 are all at the same level, D3 and D4 are slightly higher.

D8 is... at roughly the same level as D1, perhaps slightly lower (the dock at least should be the same level as D1)?

D12, D11, D10, D13 are all lower apparently.

But the tunnels are described as being below sea level, so naturally they flood when the pumps are shut off. But when the pumps are active I don't understand how they keep the place dry.

Do they pump in high pressure air to push the water out? If so, that would cause the whole area to have uncomfortably high air pressure, and any time someone would open the hatch in C16 the pressure would drop and water would rush in (making the hatch impossible to close).

And where is the water pumped into? All the water areas are connected, the pump can't move water from one reservoir into another, it can only move it around within the same body of water.

I feel like I must be missing a crucial part, but right now I feel I just can't describe this area in a way that will make sense to my players (or myself).

[roguerouge]

Well, the engineer at my table missed that, so I guess you can just wing it, then say a wizard did it if they call you on it?

Anyone have a better answer?

[Warped Savant]

They're magical pumps.
They make it so that the entire area believes it's just above sea level.
Because Magic.

[DM Livgin]

I'll enjoy describing the water flowing uphill...

I only skimmed the maps and area, I'm prepping for session 0 right now!

[Lanathar]

Warped Savant wrote:

They're magical pumps.

They make it so that the entire area believes it's just above sea level.
Because Magic.

Ha I was going to type this yesterday!

[Brenden Falke]

I'm just gonna turn the area between D8 and D10 into an airlock with double doors. That makes the system work (broadly speaking).

[King of Vrock]

Consider the tunnels to be like a diving bell. The pump pushes air into areas D1-9, but water flows from the sewers D-9 which are above the tunnels west through the dock area D-8, and out into D-13 which is below the air-filled section of the tunnels (everything East of the dotted line between D-8 and D-10.

The barrels with the bottles of air give you a clue that the exit to the river is below sea level as the Gray Spiders used charmed aquatic creatures like Chuul to move the smuggled items out of the complex.