I have tried that in the shower and also in the bathtub. It's a great feeling but impractical since as soon as you move (even a little) the diaper will leak so it's only good for the time you are in the shower or tub. I don't do it very often.
I have also gone swimming and sat in a hot tub with a disposable diaper it's an awesome feeling but don't pop the diaper or else you have a mess you don't want to clean
I've worn one in the shower. It's fun seeing it fill up so fast, but it's not really worth it. Not only does it waste a diaper but if it bursts the sap gets everywhere and a fully soaked diaper weighs like 5 times as much as normal so they get really heavy.
I've taken a bath in a disposable diaper a few times and I loved how they swell up.
While it is a fun thing to do, be very careful not to let the diaper fall apart. If the SAP gets out it's near impossible to keep it from going down the drain, and it can mess up your plumbing pretty good (don't ask me how I know).
One time I woke up extremely early in the morning and due to a power outage messing with my clock I though it was later in the morning. So what happened was I was half asleep, went into the bathroom, got ready to take a shower but forgot my diaper was on and stepped into the shower. Although already wet before, it was now more wet, heh. In truth I am half asleep while typing this so sorry for any typos.
Yup! I do it all the time! In fact, I make sure to test each & every new diaper to its' limits! If you like the waddle & swell of the diaper, then this has to be tried!