The baddies (which include a very young Melvin Wong) have a secret base on a fish farm in the New Territories. After a bit of looking around it looks as though this particular one was floating in front of Ma Nam Wat just outside of Hebe Haven. If the name of the place rings a bell it might be because this was also the area where Jack Palance filmed some of Kill a Dragon a decade earlier. There is still a fish farm in the same location today.
And here is Melvin, not far into his HK film career and already sporting his trademark moustache. I have a claim to fame in that I had the exceptionally good fortune of meeting Melvin (and his wife Angie) back in December 1996 at a mutual friend's childrens' birthday party (his son Wesley went to Shatin College with my friend's children) and all I can say is he and his family are a really nice bunch of peeps.