A chemical tanker was discharging in port and two crew members were working to top-up the air pressure in the lifeboat air supply cylinders. One crew member was in the compressor room and operated the compressor while the other was in the lifeboat to connect/disconnect the air hose to the cylinders and validate the pressure. The crew member in the lifeboat was aware of the procedure but had never carried out the task before. There was no visual contact between the two crew members and...