This is actually a rather philosophical question you have asked.
In modern sub combat, engagement ranges are extremely short sometimes relative to detection ranges and the "on paper" ranges of the weapons.
In DW 1.03 (the version you purchased), when playing the AI, in most situations you have flexibilty as to whether you want to engage at long range or wait until you are closer and have a better solution. When playing in MP, engagements typically take place at as long a range as the acoustic conditions allow minus a couple NM.
That's the short answer.
The long answer would require an explanation of game mechanics and modding that I'm not sure you are interested in.
Cheers,
David