Cleaning 30m/3atm Water Resistant Watch

Without knowing the condition of the watches it's hard to advise you. If they were recently serviced, with new seals installed, then it should be ok to submerge them and wash them gently. However, if they are old watches that haven't been maintained, the seals may have degraded and you could conceivably get water ingress at various locations, including near the crown. Unfortunately you don't know until it's too late. It would be safer just to use a soft brush and wipe them down with a damp cloth. If they have bracelets, you can remove them and wash them more thoroughly.

You are wise to ask! Before you expose them to water such as you suggest, review the service history of each watch concerned, and have them tested for water resistance. You may find a watch to be water resistant, or perhaps one that is no longer water resistant. Time to decide whether a complete service might be prudent on one that fails the test. Or with luck, you might find that replacing the seals might be all that is required.

I just use a damp cloth to wipe it down, then a microfiber cloth to dry it. That’s good enough to keep it clean until it is serviced, where the entire case and components go into an ultrasound or whatever cleaning equipment is used.