Can't remember anime where most of the earth is covered in water and theres a war between water and land peopl?

can't remember anime where most of the earth is covered in water and there's a war between water and land people. the usal grudg between sides and no one will ever get along... but there was one person a man that opened one of the tripodthingys and inside was pink slime but a very pretty girl.. i think her body was all white and had small flippers on her ancles and blue hair? thats about all i can remember.. can anyone help?