The calculated distance (air line) between Hung Shui Kiu and Sai Kung is approximately 18 miles respectively 29 kilometers.
By car or train, the actual journey to Sai Kung is certainly longer, as only the direct route (as the crow flies) between Hung Shui Kiu and Sai Kung has been calculated here.
Air line (approximately)
29 kilometers
16 nautical miles