I feel like it would have been easier for me to learn how naval units worked if they were presented one by one over the course of the campaign, like how land and sky units were presented, to better grasp how to handle them. The way it is right now, we're given the option to produce all the naval units on the fly, which felt somewhat overwhelming for the first naval map in the campaign.
The problem is that naval units are all intertwined and interdependent. Air units on the other hand can mix with ground units and can also be countered by ground units. Not saying that this is a problem in design, but you can't just introduce one and call it a day. If anything, maybe the amphibians and landers -- but the other three have to come together.
The naval game is a bit unusual, yeah. It's sorta happening in a parallel lane to the "main" battle with stakes that aren't absolute but still very high depending on the map. I think one reason turtles are balanced to be so overwhelmingly powerful in the sea is because they're the only naval unit that's totally unable to influence the map going on outside of the water. When you get down to it, there are two main goals to a naval battle: 1. Control of water villages/seaside properties and the potentially hugely game-changing amount of income they bring in. 2. Getting a beached warship into the midst of the main land conflict, whereupon it will act like a near-invulnerable trebuchet on steroids. More than makes up for the naval game being in its own ecosystem prior to that point. Also harpoon ships on paper don't look great, but two of them in the right place will completely shut down any attempt to dislodge the warship using air units or trying to bumrush with a single turtle.
