Timex Easy Reader, says 30m, failed on a dive that was no more than 15m.
Seiko SKX-007 OTOH, rated to 200m, I have taken it to about 30m with no ill effect.
I've since learned you can have a watch repair shop test this with a pressure chamber and a finely-calibrated displacement-measuring instrument, no water required.
Generally 30 meters shouldn’t be submerged, 50 meters is okay for swimming, above that diving is acceptable to certain limit. True diving watches start with 200 meters and preferably ISO diver's certification (which SKX has).
Of course I say all that and yet I have a Seiko spring drive tuna 600m saturation diver, even though it's never been deeper than a few meters and very unlikely ever to do so. But the engineering is fun to appreciate even if it'll never do even 1% of what it's capable of.