Chinese water torture
 

A nice simple dare here.

Get yourself nice and worked up. Edging several times is an excellent start for this.
Now, you want to lie on your back in the bath with your ass up against the edge and your legs spread wide or at least on either side of the taps.
Now turn the tap on just enough that you get one slow drip. Angle yourself so that that one drip lands directly on your clit or right wear your penis meets the balls underneath.
Turn the drips or down to control how long you are there for.

How long can you last