GRIPPER BARS, a SHOWER MAT, and WATERPROOF LUBE!
GRIPPER BARS: Get ADA approved gripper bars for your shower — not that the ADA rates them for shower sex. One of you can grab the bars, making shower sex safer and giving you more leverage. (If your parents are visiting and say “WTF?” tell them they raised you to be responsible and to care about safety.)
These bars cost between $25 and $46 USD: Moen 8942 Home Care 42-Inch Grab Bar Stainless 42 inches (4.8 out of 5 stars from 3,233 reviews on Amazon, but none mention sex in the shower) and the Moen 8736 Home Care 36-Inch Grab Bar, Stainless , 18″ to 42,” (4.8 out of 5 stars from 9,107 reviews).
The Moen Grab Bars are rated at 500 lbs. pull strength and are ADA compliant when attached according to the instructions.
SHOWER MAT: At least one of you will need to have his or her feet firmly planted on the ground. This is not always possible if the floor in the shower can become slippery. Be sure to get a high quality, non-slip shower mat or non-slip stickers with good adhesive. And clean it often, or really gross stuff can form under it.
WATERPROOF LUBE: Water washes away a woman’s natural lubrication. Silicone-based lube is best for sex in water, but if you are using a silicone-based lube, be sure to put it on while you are standing over a towel. One drop of silicone-based lube on a wet shower floor and you might as well be on slick ice. A fun time in the shower could quickly turn into broken bones or a nasty concussion, and a 911 call.
WARNING: These are only suggestions. Call your county planning department and ask if they have code requirements for showers that people have sex in. Be very specific when you are talking to the clerk, eg. “What if we only do rear entry” and “Does that apply to anal as well?” Also, I don’t do affiliate links and do not receive any money if you use these links. I only include links to products when I truly believe they are helpful.