Infuriating ships!!!

[Trithemius]

I find that ZOCs are very weak for everyone but me actually -on land and at sea!

I had a very similar Imperial game as Satsuma. Enemy ships really annoyed me until I:
(a) made some cruiser squadrons to engage and defeat enemy stacks - typically 5x Kasuga-class corvettes + either the HMS Warrior or some frigates
(b) made some patrol squadrons to protect key shorelines and trade routes - typically 3x corvettes + whatever ships I could capture from the enemy! :)
(c) sent a single gunboat to every enemy port, slowly following up my cruiser squadrons, to prevent ports from rebuilding or producing new enemy ships

The investment of 50 koku every turn for an enemy port was compensated for by my trade income and the ability totally run the seas!
If the enemy has a lot of military ports it can be good to keep a patrol squadron nearby to bombard them back into submission if they do get around to rebuilding though.