Over reliance on radar and ais against visual lookout, radar and AIS alarms not set or inoperative, excess speed, sudden turn, lack of radio contact between vessels to confirm intentions but most probably not enough crew on bridge or distracted by various displays on bridge. Some years ago a vessel was seen off course and not answering radio comms. Only when relief watch went to bridge was it found that the master on night watch alone had died from a heart attack. Recently a large dredger coming out of a harbour struck and sank a yacht with loss of 1 life. Only one man on bridge who did not see the yacht because he was busy with AIS or radar.