Hey Aqua!
Not matter what make sure you have your caseback and crown gaskets replaced every five years (or every battery change; whatever comes first). The rubber gaskets dry out and the best watch in the world will leak at this point. Most jewellers/watch battery places don't do this.
I buy the gaskets on the internet for pennies a piece and replace them myself and also use the proper silicone. While I don't presently have a pressure tester some watchmakers do. If you have a serious dive watch and plan to do more than swim with it ensure that you get your gaskets replaced at every battery change or movement service (in the case of automatics) and then have it pressure tested.
All my serviced watches have been pressure tested and passed. I took my 1976 6105-8110 Seiko diver SCUBA diving last month with no problems. It raised a few eyebrows on the boat!
FYI, this is the same watch Nick Nolte wore in
The Deep.Here is the watch pre-resto. Notice the missing lume on the hands:
And after some fix-ups...
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This is the watch I sometimes like to wear when driving the Chevelle. It is a restored 1969 6105-8000 Seiko diver. It is an earlier version of the above watch with some different features. BTW, like my Chevelle this was a one owner job. I am the second wner of this watch...
Pre-resto:
Post Resto: