Hi, I have a tag heuer chronograph with a screw down crown as is 200 metres water resistant.
It may require you to apply pressure to the crown as you wind it and for it to eventually 'lock' into the screwed down position as is the case for mine. This 'locked' position should become obvious when you cannot turn the crown screw any further whilst applying finger pressure to it but it should not take more than one or two full turns to achieve this position.
kevin mckeever, August 2008