This is one of the coolest ideas I've seen!
It took me one "play-through" to understand what I am doing, one more to learn and the third one to "should-have-won": my ships crossed the right part of the screen, but the game continued playing and as with the second playthrough, at some point the huge unbeatable hoard of enemy ships started (as on the photo).
Also, as already said, air ships don't work: I figured out they had to be placed (although that was unintuitive given boats are placed automatically), but air ships still don't work - they just drop bombs which don't cause any damage, neither to enemy boats, nor to enemy cannon, nor to enemy blocks.
I figured to place triangle blocks in a way so they fall and stack (as on the photo), but I think they should be rotatable.
Circle block as it is doesn't make sense: it 3 times as fast as triangle, but 6 times more expensive and to easy to roll away.