Dear,

Next to the information provided by Urs, there is also [www.uboat.net] that allows you to search for and see which uboats operated in the Baltic on a particular day.

And for such uboats you may find the most important facts of their patrol in [historisches-marinearchiv.de] (enter uboat-number with or without a data or a date-range in the search form).

Best regards,
Walter