It's easy to confuse (or forget) what particular lights, marks and shapes mean – especially under stress or in the dark – but with this handy book, help is quickly at hand. Laid out simply & clearly for quick accessibility, it enables crew, navigators, skippers and even casual day guests aboard to quickly identify the lights, marks and shapes being displayed by other ships at night as well as during the day.

A ready reckoner reminder of:
-Cardinal buoys and channel markers 
-Lights displayed by ships at night (tugs, dredgers, pilot vessels, stationary vessels, fishing boats, yachts, motorboats) and from all aspects (front, side, astern) 
-Daytime shapes displayed by boats (e.g. for anchoring, towing, diving, dredging) 
-Ships' sound signals (used in fog) 
-Signal flags and their navigational meanings (I am dragging my anchor; You are running into danger; I have a diver down).