You can shower in an RV shower as much as you want too and as long as the hot water stays hot in the water heater.
Most RV showers will use up all the hot water within 2 to 3 minutes so you're usually limited to a 2 to 3 minute quick shower before you run out of hot water from water heater.
If you're hooked up to a water supply at an RV park then you won't run out of water and can take as many showers as you want too.
But if you're using your water tank then you'll be limited to the amount of water in the water tank before you run out.
Usually you can take around 5 or 10 showers on a tank of water if they're short showers but you may also want to save some of the water for other things as well especially if you're unable to refill the water tank soon enough.