You have a long but interesting tour ahead of you.
I suggest that you visit the following site:
[www.uboatarchive.net]
Therein you will find daily reports of U-boat positions.
The Caribbean area positions will be given with a designator such as: DL DN DN DO followed by numbers. That site also has a selection of items /articles about individual boats.
Google and this present site can help you to find a U-boat Grid Map which will show those positions
You can access a decoder at www.navalgrid.com, which will convert the Grid designators to Latitude and Longitude.

Good hunting

Phil