Depends on what you're looking for.
For basic wargames, there are 2-d card style available from
Junior General Home Page - several different ones under "Battle of the Atlantic". The site has actual games to use with these cards. I found the site when my son needed trireme models to use in his Interpretive History class.
The Canadian Navy also has several relevant 2d models on their website.
Canadian Navy: Canadian Naval Centennial - Downloads
Meanwhile, JSC has a 1/400 scale Victory Ship and a number of related vessels.
JSC - paper models ships vessels aircrafts architecture
If you want a totally detailed Liberty Ship - Halinski's 1/200 scale model of the Jeremiah O'Brien is quite a challenge, but I've seen good results. Unfortunately it is out of stock at Halinski right now.
Olli has some very relevant models here.
Ships/ Military and Zivil - Olli's Papermodels
Hanamaga is an old favorite - with numerous links that may be relevant.
50 ‘D”•
There's even a model of a u-boat base that you can find here.
U-Boat Pen Diorama