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SARB is a good shout, I would have suggested one of the new "zen garden" ones but they come in at either 38mm (eg https://www.seiyajapan.com/collections/seiko/products/seiko-automatic-presage-sary149-made-in-japan) or nearer 42mm (eg https://www.seiyajapan.com/collections/seiko/products/seiko-automatic-presage-sary141-made-in-japan). The SARB was 38 too though.
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I think there are quite a lot of options that fit the bill, but are only gonna be found by hunting.
Swimming doesn't really require massive m's or a screw-down crown. Quartz is probably the best way to keep thickness down though.
I guess the best bet is to try the zen gardens in the flesh though, as it's always surprising how differently a watch can wear depending on design.
Have a look at Tissot.
This may be a bit thick:
https://www.creationwatches.com/products/tissot-247/tissot-t-sport-prc-200-powermatic-80-t055-430-11-047-00-t0554301104700-mens-watch-11432.html
Harder to find now but Seiko Sarb033 is a nice dressier option, which works on a bracelet, smart strap or a more casual strap to change the look: