Fighting the U-boats
The Four Pipers
The most interesting variant of those were the flush-deckers (or "four-pipers") of WWI vintage that got pulled out of mothballs and 50 of them were sold very expensively to the British (8 of those went to the Royal Canadian Navy). They were ill-suited to hunt U-boats due to their age and lack of modern equipment, yet they served all over the North Atlantic. These ships were known as the Town class in the Royal Navy.
The Four pipers in mothball in the United States after WWI