MAP02: Underwater Explosions (BTSX-E2)


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Secret map: 31

This level occupies the map slot MAP02. For other maps which occupy this slot, see Category:MAP02.

MAP02: Underwater Explosions is the second map of the second episode of Back to Saturn X. It was designed by Tango and uses the music track "Depth Charge" by Stuart Rynn. In the official add-on version, this level's name is Depth Charge, taken from its track title.


Map of Underwater Explosions
Letters in italics refer to marked spots on the map. Sector, thing, and linedef numbers in boldface are secrets which count toward the end-of-level tally.


As its name implies, this level features a large number of barrels that can and should be detonated to kill enemies.

Head straight forward until you drop down a hole, then turn right and follow the tunnel to get outside. Turn left and head towards some steps to find a shotgun and/or shotgun guy as well as some imps, then go round the corner and quickly blow up the barrels here to slay the imps and zombies ahead, as well as a Hell knight around the next corner. Head round that corner and enter the water, then push past some imps to a crucifix button in the north-west corner and press it to raise a lift behind you - this will also cause demons, imps and a revenant to teleport in to the water. Ride the lift up and enter the doorway straight ahead to enter another water pool, turn right and blow up the barrels ahead to kill as many waiting enemies as possible, then go to the south end of the pool to find another crucifix button - watch out for an arachnotron and one or two chaingunners that appear on the ledge behind you. Press the button to open a door halfway along the pool, then go through this and look at the left-hand window to see a doorway leading to the red keycard.

Go back to the pool entrance and open the red key door to find a super shotgun, an armor and a button that will lower a lift just behind you. There are imps, demons and one or two arch-viles waiting in the room above - you may wish to enter the room to alert them, then step back on to the lift and blow up the barrels to catch as many of these monsters as possible. Go to the east end of the room to find the blue keycard sitting in a window, dispose of a couple of revenants that teleport in then go to the west end of the room to find a button (indicated by a candle) that will lower the lift you used to enter the room, allowing you to leave. Backtrack to where you faced the first group of enemies and open the blue bars here, then follow a hallway past some chaingunners to enter a semi-circular room with a blood pool. Press the button by the south wall to open a lift on your right, ride it up and dispose of two arch-viles and two chaingunners on platforms before running across the square pillars to a waterfall, which will end the level.

Other points of interest[edit]

Before entering the water pool with the large lift, you can drop into another pool to the south that holds demons, spectres and a berserk pack.


  1. Across from the starting area is a platform with a candle that is only accessible by a precise strafejump, with two sets of shotgun shells. Once you fall into the gap below, this secret becomes unreachable. (sector 409)


An exploding barrel (Thing 677) has no flags set for any of the three difficulty classes, so it does not actually appear in the level.

Demo files[edit]

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Routes and tricks[edit]

Current records[edit]

The records for the map at the Doom Speed Demo Archive are:

Run Time Player Date File Notes
UV speed
NM speed
UV max
NM 100S
UV -fast
UV -respawn
UV Tyson
UV pacifist

The (absence of) data was last verified in its entirety on February 21, 2022.


Map data[edit]

Things 790
Vertices 2559*
Linedefs 2618
Sidedefs 4011
Sectors 444
* The vertex count without the effect of node building is 2055.


This level contains the following numbers of things per skill level:

Technical information[edit]

Inspiration and development[edit]


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