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I routinely replace batteries on my Citizens. Batteries and o-rings are available. A case-back wrench is advised .... if it's an older model it probably has tiny screws.
I like a nice, reliable watch that is not so expensive I'm afraid to dive with it. I have been diving a Citizen Aqualand Eco Drive for years now and love it. The battery is solar powered so you never have to replace it and the second hand turns into a depth gauge during dives which makes a nice back up to your primary depth gauge.