“Water surface activities” ie swimming = 100m and up. You can submerge it fine, but it’s the momentary localised water pressure from hitting the water that a 50m rated watch might not like.
I wouldn’t swim in a mechanical chrono (unless it was designed as a divers chrono) or a watch without a screw back and crown, especially if it was worth anything.
“Water surface activities” ie swimming = 100m and up. You can submerge it fine, but it’s the momentary localised water pressure from hitting the water that a 50m rated watch might not like.
I wouldn’t swim in a mechanical chrono (unless it was designed as a divers chrono) or a watch without a screw back and crown, especially if it was worth anything.