The problem I have with the rising water theory (and maybe I don't know what I'm talking about) is that ice is, after all, water. Water has the same volume as ice - it's just frozen water with trapped air. So, water volume is what water volume is. Even if all the ice in the world melts, it will still be the same level because the water isn't increasing. If you dont't believe me try an experiment. Just fill a glass half full of ice and fill the rest with water until it's at the very top. So that one more drop would overflow. Then put something under the glass to show if water is leaking out, like a paper towel. Then wait till all the ice melts. It won't overflow - I promise.