Ship-ship collisions have the potential to cause catastrophic marine accidents with human and economic losses as well as environmental pollution. Safe navigation is a major operative task for the officer(s) on the watch (OOW) as the ultimate responsibility for safe navigation resides with the human navigator. Though the universal use of automatic radar plotting aid (ARPA) system on board ships has greatly reduced the maritime collision risks, it brings the OOW great burden for collision risk assessment and in the planning of suitable evasive actions in complex situations (e.g., many targets approaching own ship simultaneously). This paper concerns the development of a direct perception interface that displays collision danger lines (CDL) and collision danger sectors (CDS) to acquired targets for the OOW to enable a quick collision risk assessment and plan evasive maneuvers well in advance of a developing situation. A preliminary experimental study of this display has been conducted. The results showed that CDS display had the potential to improve navigators' performance compared with ARPA display. Further study is required to investigate the merits and demerits of this display.