I agree with Jim newer diver's tend to rely on these computers and bottom timers and they can fail. I think everyone should be able to know the table's and be able to dive with or with out computer.
As falman states a real diver uses mechanical dive watch.
I wish I had a girl that was smart and wanted to get me something that reminded me of her when I looked at it....
Not being a real diver, I tend to rely more on an electronic bottom timer than a watch. I do use a computer sometimes, too.
That is partly because I am worried about failures. I once had a mechanical dive watch that I used with students in pool instruction. It failed twice before I threw it away. Strangely enough, it would stop working for 10-20 minutes and then start again. That's a bad failure, because when you look at it you have no idea that it is incorrect because it is still working. If it had just stopped, it would have been much better.
My Seiko dive watch had a part recalled because it would cause the watch to fail unexpectedly.
I don't know where people get the idea that mechanical watches don't fail.