Many warships are present in their historical theatre of operations. More info you may find in GWX 2.1 manual. Those informations are rather acurrate.
There're many posts concerning this subject on the forum. All you have to do is ... to search

. Warships may be found in harbours f.e: Scapa Flow, Loch Ewe, Reyjkjavik, New York, Gibraltar (my favourite), Alexandria, Port Said. You may check movments of large or small Task Forces using SH3 Campaign or Mission Editor Tool attached to your game. For more info how to use it - check posts on the forum

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The best area to meet Task Force is Med. theatre of operations, especially from mid 1942 to late 1943.
You can check this thread:
http://www.subsim.com/radioroom/show...hips+locations
or
http://www.subsim.com/radioroom/showthread.php?t=140610
Good reading, .... and good hunting