id say a good inch or two
mine...well, didnt care about anything
lol, i put him in about an inch an a half - two inches of water, and he sat there, i thought he was getting used to it, so i waited to see if after a while, he'd move, but nope, after 20 min. the water cooled a couple degrees, so i took him out, and put him in his cage, havent soaked since