See that water in the image above?  You can dive into it.  In fact you'll be spending half of your time under those waves... this is a retelling of The Little Mermaid after all.  The massive denizens that occupy the land are spawned from those icy depths, and they know no bounds when it comes to hunting their prey.  The world beneath the surface becomes especially treacherous the more Pisces becomes human... it's hard to survive under water when you need air to breath. 
The tides of time have drowned the world, and there's plenty of valuable items hidden in the crevices of the ocean floor.  Sunken ships, cities, and technologies hold the keys to defeating your foes.  The only way to reach them, is to dive in.