Good question, I know that LW has customized the active sonar frequencies quite a bit, its probably important to know what frequencies correlate to what boats...
... in a pdf format would be great as well, that way it could be handy at alt-tab for quick referencing (on a side note....hm... I really need a 2nd monitor to be able to reference without alt-tabbing out of the game :|\ that would be :|\ :|\