Will this force me to go?

If I took a 8 ounce plain water enema bulb could I just hold it in for 3 hours since it's just water?

That shouldn't be a problem. If it is, then wear a plug.

It is possible you could hold it that long being only 8 oz but chances are you won't be able to. If you want to try don't do it if you are full go to the bathroom first and then take the enema high and use knee chest position hold the position for a wile and you will have a good chance of success and possibly you will absorb the water or some of it anyway if you get to hold it that long. Let us know how it goes.

It may be that in 3 hours such a small amount would be absorbed both both by the stool as well as the colon/rectum. Why are are you trying to retain? That volume is about twice a fleet isn't it?

I'll be nice and refrain from evil comments. (For once)