Thank you both for your responses , he didn't say what the reading was when it failed. I thought that the moveable bezel could be taken off without interfering with the seal of the watch. I must apologise to the forum as I now realise this is for people with a real interest/passion for horology rather than to respond to one off questions from a muggle like me.
I have quite an old ladies TAG watch that has had the battery replaced several times previously by The Watch Lab. Today I took it in and was charged £79.95 for a new battery, seal and test which had to be paid up front. When I collected it I was told that it failed the test twice so could not use underwater and this was because of a wobbly bezel. It wasn't wobbly when I took it in and he said it would need to go to the service centre (presumably at additional cost) to resolve the problem. Any thoughts please as to what I can do now and does a wobbly bezel actually affect the sealing of the watch. Thank you in advance