New SubC - crown not flush

[Andad]

The Daytona has no screw down crowns on the pushers.
It has internal 'o' rings on the pusher stems.
Yet it is waterproof to 100 meters + a good safety margin.

How does your watchmaker explain this feature?

Your watchmaker is correct in that if the crown is not screwed down and the internal 'o' ring are worn then the watch is no longer waterproof.
Probably why he sees some with water damage as users splash around in the pool.

It the internal seals are worn and the crown is screwed down then the watch might be waterproof to a few feet but not to rated depths.

The pressure on a watch at 300 metres is around 450 psi and a finger tight crown seal would not hold that pressure.

Serious depth divers can be counted on one hand and watches worn by them would be tested to rated depth.