What would it take to make water fun? [Discussion]

Disclaimer: I know, no changes like this will be made, this is just for the sake of discussion.
I guess water never was supposed to be the main focus of the game, but just have a supplementary function as additional options, and I do think on maps like Nomad, and golden swamp it works really well that way. It changes up the game play and gives you additional options.

But then you have Island maps, just completely dominated by water, where just the same unit is spammed over and over, until someone does not have any ressources anymore. Only times this really is changed up, is if someone manages to land on the other island early. But that rarelly happens.

So on land the unit are extremely variable, whereas on water you basically only have the equivalent of farmers, Cav archers, Camel Riders, Bombard cannons and well demo ships (actually useful flaming camels?).

So what would it have taken to make water only battles actually interesting to play? Would it be enough to add a ranged counter to Galleys (equivalent to skirms or mangonel), or would it need more than that? Maybe an additional production building even?