Thirty metres means splash-only. Per Omega's manual, the Moonwatch's 30m / 3 bar rating covers rain and hand-washing — not swimming, showering, or diving. Hot water, steam, soap, and salt water all attack the gaskets. Treat any vintage Speedmaster as effectively zero water resistance unless freshly pressure-tested.
Water: the iron rules
- Crown always pushed fully in (position 1) — around water, this is non-negotiable.
- Never operate the crown or chronograph pushers underwater. Doing so opens a direct path past the seals.
- Owner practice varies — some swim with modern examples without incident — but the official guidance and the watchmaker consensus agree: don't.
- After any salt-water exposure (which shouldn't happen, but life happens), rinse with fresh water.
Magnetism: fast, not slow
- The 1861/861/321 families are vulnerable to magnetism. The 3861 (Master Chronometer) resists 15,000 gauss — for practical purposes, a non-issue.
- Symptoms: sudden fast running — +10 seconds a day to minutes per day — occasionally with chronograph hand jump or stoppage.
- Everyday sources: magnetic phone and tablet clasps, speakers, bag clasps, tools, flashlight magnets.
- The fix: a demagnetizer — inexpensive, harmless to try. As one watchmaker puts it: if it slows down, it was magnetized; if it doesn't, it wasn't. Demagnetize before assuming a service is due.
Storage
- Dry, stable temperature, away from magnets, speakers, and prolonged direct sun and heat (gaskets and lume both suffer).
- A watch box or roll does the job. No need to keep a safe queen running — letting it rest unwound is fine; oils age whether it runs or not.
- Some collectors give stored watches a wind every month or two. There is no strong evidence this meaningfully extends lubricant life — do it for pleasure, not chemistry.
Watch winders: pointless here. A winder rotates the watch to swing an automatic's rotor. A manual-wind Speedmaster has no rotor — rotation does literally nothing. You turn the crown by hand to charge it, winder or no winder. Save the money.
Cleaning
- Wipe the case with a soft cloth.
- A metal bracelet can take a soft toothbrush and soapy water — then dry it thoroughly.
- Keep solvents, perfumes, and harsh chemicals away from the watch.