Perhaps influenced by post-WW2 Royal Navy practice, it has long been the accepted wisdom that all the bottoms of RN warships during the World War 2 era were red. This turns out not to have been the case. The result of over four years research, this book reveals the information concerning the treatment of the lower hull, including the boot-topping area, of every RN, RCN, RAN, RNZN, RIN, FNFL, KNM and RNLM ship of the WW2 era for which records were found in UK archives. Additional information from Canadian and Australian archives is also included. At the book’s heart is a ship-by-ship reference list with details of the painting of the lower hulls of over 850 surface vessels and submarines. The details in this list can be combined with the background information in the narrative chapters and other guidance in the appendices to enable the reader to make an informed decision as to the likely colour of the bottom of most of the ships listed at any given time even when the colour itself was not noted in the archived records. It is an invaluable reference for those striving for accuracy in depictions of these warships.