Looking at the facts
The terminology water resist has to meet, since 2010, the following ISO norm IF you want to mention the water resistance on the watch itself, next to all the tests and requirements
ISO 22810:2010, Horology – Water-resistant watches , has been drawn up to meet a global demand for clear and unambiguous specifications in this area. It clarifies the terms used, defines the criteria to be met by the product and specifies the marking which may appear on the product.
That means that 50 mtr ofr5 bars signifies that you can swim with your watch:
Water resistance rating Suitability Remarks
Splash/rain resistant is not suitable for showering, bathing, swimming, snorkeling, water related work, fishing, and diving.
Water Resistant 3 atm or 30 m is Suitable for everyday use.
Water Resistant 5 atm or 50 m Suitable for everyday use, showering, bathing, shallow-water swimming, snorkeling, water related work, fishing. Splash/rain resistant. (
https://en.wikipedia.org/wiki/Wikipedia:NOTRS 1) Not suitable for diving.
Water Resistant 10 atm or 100 m is suitable for recreational surfing, swimming, snorkeling, sailing and water sports. Not suitable for deep water diving.
Water Resistant 20 atm or 200 m is suitable for professional marine activity, serious surface water sports and skin diving. Suitable for skin diving.
Diver’s 100 m Minimum ISO standard (ISO 6425) for scuba diving at depths not suitable for saturation diving. Diver’s 100 m and 150 m watches are generally old(er) watches.
Dynamic movements adds pressure trhough movement in thin fluids, and if you want to skip algebra, the last sentence says that it will not addup to more then half a Bar, of 5 mtr by swimming with your watch:
Dynamic pressure is the pressure induced by movement in dense fluids, in the case of a diver typically the pressure caused by his swimming movements in water. A dynamic pressure of 1 standard atmosphere (100 kPa) (for example the flow of a river) on the surface of a hand (assuming the surface of an “average hand” of 150 cm2) will correspond to a dynamic pressure induced force of 1,500 newtons (340 lbf). In order to calculate the dynamic pressure caused by a fast underwater swimming movement of a diver the following formula can be applied:
P = 1⁄2 ρv 2
Where P is the dynamic pressure, ρ is the density of the fluid and v is the speed. For a fast swimming movement of 10 m/s in typical sea water this works out as:
ρ = 1026 kg/m3
v = 10 m/s
P = 1⁄2 × 1026 kg/m3 × (10 m/s)2 ≈ 51,300 Pa ≈ 0.5063 atm
This calculation shows that fast swimming movements will not create dynamic pressure surges exceeding 0.5 standard atmospheres (51 kPa) (the equivalent of 5 metres of water pressure).
Swimming 10 mtrs (33 feet) per seconde is about 36 km/h (22 miles/h) an that is quite hard to do
…
Omega says this:
All current OMEGA watches are water resistant to the depth defined by the model specifications, provided that the components ensuring the water resistance are intact. This means that an OMEGA watch that is water resistant to 30 metres can be worn for swimming at depths of up to 30 metres underwater for extended periods without restriction.
https://www.omegawatches.com/customer-service/faq
IWC says the same thing:
https://www.iwc.com/nl/en/specials/water-resistant.html
So by definition Patek 30m is swimable, and if they state that the watch can actually survive 30m under the surface the that would be a huge upgrade