"....where did the water come from?"

Iona provided the explanation....It rained..

from her link: "the "great deep" which was "broken up" evidently speaks of great subterranean reservoirs or chambers deep inside the earth, all of which spewed forth their contents at the same time. "

Simple, hmmm?

...except for the math and geological pre-suppositions required to clarify where "great subterranean reservoirs" got there, and how they re-absorbed all the water after 40 days....

And STILL she says "There is tons of evidence for creationism. I've posted a lot already!"...using a Biblical definition of 'evidence'.