This portion of the Luigi’s Mansion 3 guide covers the Boilerworks Walkthrough and all the Boilerworks gems (note: not all of these can be collected on the first run so you’ll have to come back regardless). Here, you’ll find step-by-step solutions to all the sewer puzzles plus tips and tricks for how to beat the mechanic boss while on the duck floaty.
The Boilerworks floor requires Gooigi and Luigi almost evenly. This is something to keep in mind if you’re co-oping the campaign alongside another player. The majority of the level requires you to get good at navigating the waters on a duck floaty but move with caution, one pop and it’s instant death.
Source: IGN.com Luigi's Mansion 3 Guide: Boilerworks Walkthrough