Its a bit hard to give a proper answer as you are at the beginning so the reasons it happens might be a few different ones Since from other information in the comments you say that this happened during the pool sessions of your course and you are not certified yet, I don't think is ok giving you too many tips about what to do, or suggest you to use one ...


I've found that just pressing my mask at the bridge of my nose after clearing or otherwise fiddling with it helps push out excess air and reseat it. But I do it immediately, instead of after 5 breaths.

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