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