M-WATCH Mondaine are water resistant to 30 or 100 metres as indicated on the case back. The water resistance rating of a watch does not take into account the ability of the watch to STAY water resistant as of ages. Therefore, the water resistance of a watch cannot permanently be guaranteed. It may be affected by ageing of gaskets of by accidental shock to the crown or pusher. Do not under any circumstances open the watch by yourself.
Make sure not to activate the time setting crown and/or pushers while the watch is under water and make sure that the crown has been pushed in or screwed down.