With spending money to earn passive money, this kinda feels like an idle game (I love idle games so no issue here :D ). I love the idea behind this, seals fighting off sharks tower-defence style.
I wish there were more types of seal to unlock, and also that the enemies would scale up a bit. I put a couple of attack seals at the beginning and they could handle pretty much anything, leaving me free to fill up the rest of the map with money makers.
Solid foundation here, played for quite a while just enjoying watching the numbers go up, great job!
(-Joe)