From 1983, the standard Royal Navy issued dive watch switched to a quartz movement. However, there also exists a mechanical automatic dive watch bearing 1984 issue markings, and produced in a batch of 100 watches (from observed case back issue numbers).
The watch does not look like any of the other 1980s CWC dive watches; it is in a different style case and is of a notably lower quality, the logo on the dial is a strange variant of the previous sans-serif logo but in an oval, and the movement is different to the ones used in 1980 and 1981. The case is an Airain France case - which is another brand name owned by Dodane - and a Dodane family member appears to have confirmed that they made "CWC" watches in 1980 and 1984. The handset is similar to the 1980 dive watch, as is the small circled T in the lower half of the dial, which would also suggest they came from the same maker.
These are generally thought to have been a special order for a British military unit in Hong Kong, as many have been found in Hong Kong or nearby countries (hence the "Hong Kong Special" nickname).
Given how different this watch is from all other CWC dive watches, there has long been debate about whether this watch was actually supplied by CWC. Ray Mellor was categorical that CWC did not supply the watch. "It’s obvious - if the movement is somebody else’s or one that we’d never used, the case is made by a casemaker who knew us but didn’t necessarily know what it was being used for, and if the dial is marked with CWC not by us, then it’s a fake!"