hanging out at a workbench on the work bench other side of the room.

Never do that unless you want to rust your newly serviced movement! You need a dry/wet pressure tester (like a Bergeon or a cheaper hobbyist clone). Here is the safe way to do a wet test:

Here is the safe way to do a wet test:

1. You hang the watch above the water level inside the sealed chamber.

2. You pump air into the chamber to increase the pressure (say, 3 atmospheres).

3. You let it sit for a minute. If the watch has a leak, high-pressure air will force its way inside the watch case.

4. Then, you submerge the watch in the water and slowly release the air pressure from the chamber.

Ah! So if air got trapped inside a leaky watch, it will now try to escape because the outside pressure is dropping?

Exactly! You’ll see a steady stream of bubbles shooting out of the leak point (the crown, the crystal, or the caseback). Because you pull it out of the water immediately, the internal air pressure actually keeps the water out while you find the leak. It’s brilliant. If there are no bubbles, your seal is perfect.

Man, that makes so much sense. I feel way better about tackling this now.