According to Rule 5 of The COLREGS (1972), requires that "every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision”.
It’s a cliche, but a cliche for a reason when we say that the mk1 eyeball is still the best means of maintaining an effective lookout. Far too many mariners get glued to their electronic box of tricks or their chart table and they forget to take in the real world from the deck.
In addition to actually looking (with or without binoculars), an effective lookout will include using all means at your disposal. This will include radar, AIS and a radio watch. In poor visibility, your ears are also very helpful.
Radar is very useful, especially in poor visibility, and it can be used, together with your charts and your depth sounder to establish a fix from landmarks, determine whether or not you are on collision course with other vessels and the location and direction of rain squalls. Many radars now overlay on electronic charts and can be used effectively in conjunction with an overlay from your AIS.
AIS is a very useful means of identifying other vessels, their type, course and speed as well as their name, call sign, MMSI number and, perhaps most importantly, their CPA (Closest Point of Approach) and TCPA (Time to Closest Point of Approach). This greatly reduces uncertainty, especially when crossing busy shipping routes or a TSS.
When using AIS, remember that the information you are viewing is only any good to you if the vessel broadcasting the information is broadcasting accurate information and that information is refreshing regularly. Old data can be misleading and dangerous! Having access to call signs and MMSI information can be very helpful when you need to make contact with another vessel, especially as many ships tend not to answer calls on CH16 for collision avoidance.
Make sure to check that your own vessel is properly presenting itself. Do you have radar reflectors in place and if you have echo max is it turned on? Are you showing the correct navigation lights, day shapes and sounds? Is your VHF being monitored on CH16 and any other channels that may be relevant such as port traffic? And finally, make sure to keep detailed logs for navigation, weather and radio communications and inform your skipper in accordance with his standing orders.