Naval challenges created by predominantly land powers

Which mostly land-based powers produced ship types that were especially difficult for maritime opponents to counter?

American heavy frigates, German S-boats, and France's early submarine force all created notable challenges.

A predominantly continental power can still produce a difficult naval threat. The United States' heavy frigates in the Age of Sail and German S-boats both demanded serious counters. The French submarine fleet around the turn of the twentieth century was another potential British problem, even though the Royal Navy was already working on responses. A focused asymmetric type can matter without its owner possessing the world's strongest balanced fleet.