In the "wild" they live in springs around 15 feet deep so I say you can fill it all the way up and make an above tank basking area! Make sure you post photos when you're done with the project.
thanks for all of the help,in a few months when i get it set up i will take a few pics.i still dont know which turtle i should get i what a water turtle that would be fine in a 55 gallon tank.
in everybody is woundering why a 55 gal is as big as i want i live in a trailer and i know the floors wont hold a 120 gal tank,or i would get a redear slider