Making non Rolex vintage watches pressure test/swimming worthy again?

[dexvd]

So I have had the idea of having a chunky non-Rolex vintage dive watch for a while but would want to actually use it for what it was meant for (probably not diving but swimming in the ocean and snorkelling).

The thing is, the common refrain; "don't swim with vintage". There must be some watches out there that have the parts availability to replace the gaskets and make them water worthy again? If Rolex can make my watches from the 60's and 70's waterproof and pass the pressure tests than why can't another brand's watch be made just as waterproof?

Has anyone looked into this or done this?