Only one can enjoy the hot water at once.
Getting soap in certain places feels like FIRE.
For those who wear makeup, better hope your partner is into pandas.
Water washes away natural lube...
Oral sex basically turns into waterboarding.
If you have a height difference it's going to be a serious problem.
Lastly, "Slippery when wet" does not just apply to roads.
That all said, it's still a pretty fun time.