Just an unpopular tidbit I always feel duty-bound to mention: confusingly "depth rating" has little to do with depth, rather it's more about pressure & immersion, and it has a LOT of caveats even for dive watches.
As background, I spoke with 2 different Omega watchmakers about this, 1 in Zurich who trained & worked at HQ in Biel for 10 years, another whose been working in Biel for a few decades. (I've also spoken with Sinn staff, et al)
All have said nearly the same thing,
assuming great condition / recently serviced, ie good gaskets:
(1.) Pushers & crown. No matter the rating, don't operate the pushers or crown underwater and, ideally, not until you're certain the watch is dry
(2.) 30m = "daily use" and/or can tolerate splashes from hand-washing, rain, etc but should not be submerged or used for swimming, e.g., most Swatches, some speedys, other omegas, etc
(3.) 50m = "daily use & light swimming"; this is where the pressure becomes important because all kinds of daily activities can create water pressure: showering, faucet sprayer, diving e.g., diving board, surfing, water skiing, hot tub jets, pressure washers, water guns, etc etc. The Omega guys said the Speedy's "50M" rating is better than most others, and speedys can
likely be used for pool swimming (ie laps) with no problems but everyone said the same thing:
(3.a.) it'd be dumb to wear it scuba diving or during any water sports like surfing,
(3.b) they'd personally take it off if there's anything that makes water pressure, and
(3.c) if you use it for swimming or routine submersion, especially chlorine or salt, get the gaskets replaced yearly. (see #5 below)
(4.) 100M = "more margin than 50m"
(5.) Any rating. If you use any Omega watch for swimming, and especially water sports, take it in to an OB yearly for free* testing where it'll also have the gaskets inspected & replaced if needed (*though this is what the Swiss guys said and I can't say they speak for all OBs)