Two amateur divers from the disciplined services were injured, one severely, after they were hit by the propeller of a speedboat during a practice run in Sai Kung on Sunday. Lai Chun-sin, 30, a Fire Services Department probationary station officer at Lau Fau Shan Fire Station, and Choi Wai-kin, 29, an officer from the Correctional Services Department’s Shek Pik Prison, were diving near Tsim Chau off Tai Long Sai Wan at about 3.30pm when they emerged and were hit by an 8.5-metre speedboat. Lai’s chest and legs were struck by the propeller, sustaining severe injuries. Choi also suffered leg injuries. Their friends, who were on a leisure boat, called for help. The duo were airlifted to Pamela Youde Nethersole Eastern Hospital in Chai Wan by a Government Flying Service helicopter. There, Lai underwent surgery, which was completed early Monday morning. Choi was said to be in a serious condition. Lai was reportedly a more experienced diver and had been guiding Choi. The speedboat driver, 53, and his son, 22, were arrested for endangering the safety of others at sea. Their boat was detained at the marine police east division base in Sai Kung. The marine police regional crime unit is investigating the incident. The Fire Services and the Correctional Services departments said their welfare staff were in touch with the victim’s families to provide assistance.