I want to get high even though I'm the designated driver
How high do you intend to get?
As much as I want but not too much that it will impair my driving.
I hear you, but if you are the designated driver you should be able to drive, so you cannot be intoxicated or under the influence. Otherwise you might get into an accident and will hurt a lot of people including your friends.
Do you think a water bong would be less impairing? I heard the high from using those wouldn't last as long.
You need to stop, you can get high after you are done driving. But it is really dangerous to drive impaired even if it isn't from drinking.