Exploring the subterranean depths of the Boilerworks in Luigi's Mansion 3 presents players with complex environmental puzzles and hidden secrets. Finding all six B2 gems requires clever coordination between Luigi and Gooigi, as well as revisiting the floor after acquiring key story abilities. This complete guide details the exact steps needed to clear the floor and secure every collectible gemstone hidden throughout the watery basement.
Elevator Hall and Observation Room Gems
The Elevator Hall conceals the yellow gem behind a hidden wall structure. Send Gooigi through the pipe on the right wall to reach the upper ledge where the collectible waits.
Inside the Observation Room, direct your Dark-Light Device toward the back corner to reveal a missing water heater. Flashing the Strobulb at the green light on the coffee machine will cause it to overflow onto the console, unlocking a hatch containing the blue gem.
Sewer Navigation and Storage Room Secrets
Reaching the red gem in the Storage Room requires manipulating water levels using valve controls. Have Luigi turn the valve to stop the leak while Gooigi travels through the left pipe to reach the lower level safely.
The green gem rests near the ceiling in the Sewer B section after the water is fully drained. Position Gooigi on the rising platform while Luigi pulls the chain mechanism to lift him close enough to vacuum up the hanging treasure.
Submarine Puzzle and the Secret Gem Ghost
In the flooded lower area near the submarine, Gooigi must enter the hatch to solve a thermal puzzle. Vacuum the flaming wood log to ignite the stove under the pot, boiling the water to release the purple gem.
The final white gem becomes available during your return trip to the floor with Toad. In the Old Reservoir area, grab a paint bucket and splash the upper wall to reveal a hidden ghost silhouette. Defeating this Gem Goob drops the floor's last remaining collectible.
