Slugs in the Shell starts with John Brown during Glugging From the Deep. Go into the cannery processing room, inspect the shell crate with the faint chalk mark, and return the contraband evidence for 1 Prize Token.
How to start Slugs in the Shell
Once Glugging From the Deep walkthrough is active, go back to the P.I. Office hub and talk to John Brown.
This is one of the late-game side jobs, and it shares the chapter with Friends in Deep Places, so it is worth slowing down for cleanup.
Walkthrough
Reach the cannery
Progress through the mission until you enter the old cannery and its main processing spaces.
Find the marked shell crate
Inside the processing room, look for the open crate full of shell casings. The target shell is tied to the crate with the faint chalk mark.
Inspect the contraband shell
Interact with the crate and take the marked shell to finish the side-job objective.
Rewards
Slugs in the Shell rewards 1 Prize Token when you report back to John Brown.
It is a short detour, but it is still important if you are using all side jobs guide to track every missable objective.
FAQ
Is Slugs in the Shell in the same mission as Friends in Deep Places?
Yes. Both are tied to Glugging From the Deep.
Do you need to inspect every shell one by one?
No. The relevant interaction is the marked crate in the cannery processing room.