To support the above comments - busy but very interesting harbour, also very nice islands on the east side of the New territories. The marina situation is mainly "overload", too many yachts for the available facilities though the yacht clubs do have visitor policies. You may find them on Google
and Jimmy Cornell's site has a pretty complete listing.
I actually live at a marina, Hong Kong Gold Coast, on the west side of the New Territories which caters for a variety of boats from jet skis to mega yachts but, oddly amongst Hong Kong marinas, is only approx 50% occupied.
Royal Hong Kong, Hebe Haven, Aberdeen and Discovery Bay normally have no available marina space but may accommodate visitors on moorings.
I can enquire locally on availability if you give me some specific dates and contact info.