For the Bathroom, with you computer
Put the shower hose up your ass, but make sure you are in a position you will be comfortable in for a while. Turn the water on, but only a little bit so it is trickling into you ass. Then, watch a movie or some porn on your computer, as the water slowly fills you up. You have to watch at least 1.5 hr's before you can turn off the water. If you last the 1.5 hr's, you can cum, but expel that water as you cum. If you have to stop before then, you must Not cum, and try again. You cannot cum until you last the whole time!
Have fun, and let me know how it goes.