Anyone have a recommendation on a water/mess proof mattress cover? Was looking at this moving cover on Amazon but would like to hear what others have used successfully. Thanks!

https://www.amazon.com/UltraBlock-Mattress-Bag-Moving-Storage/dp/B07D6WQFCP/ref=mp_s_a_1_12?keywords=waterproof+mattress+bag&qid=1652930705&sr=8-12

Try searching for water proof mattress covers, my wife and I bought one a few years ago, the only downside is ours is only waterproof on top or the center of the mattress, if anything drips on the sides it will get on the actual mattress. So now we use it on our air mattress it works great and we just throw it in the washer when done.

I use a PVC bedsheet; it feels great to slide around on, fully waterproof, and easy to wipe down.
(literally designed for the job of messy sex)

The downside is the one I brought doesn't quite cover a double bed, so I put a polythene dust sheet under it.

Cool, thank you for the suggestions!

Nuru mattress covers are the best.

Here are a couple :
https://www.nuruplay.com/products/nuru-play-king-size-bed-protector-pink

https://nuru-guru.com/products/mattress-protector

Not sure what brand we have but my wife wanted water Proof covers cause I overly sweat at night and don't have AC. I sweat so much it goes through both sometimes so just make sure you check before using it for wam.
We buy cheap dollar store table cloths to line our bathtub so clean up is easier so maybe tarps that r thicker r better?

My wife wanted something that felt like fabric rather than plastic. Used a waterproof mattress protector from Dunelm Mill for a while - you can get ones where the top feels like brushed cotton. However, they're only available in white, so it ended up looking rather discoloured after a while, and also they don't protect the sides of the mattress - the fitted elasticated bit isn't waterproof. So recently we've just used an ordinary grey sheet put over a cheap painters dustsheet. The dustsheet usually needs binning after each session, but is only a pound or so, and the sheet has so far been washing up well each time. And no leakage through the dustsheet - although the polythene is very thin, having the fabric sheet over the top seems to protect it from ripping.

PVC or vinyl sheets you can find online from fetish companies. Those work the best. The only thing is to be careful for runoff, those slick sheets help move runny substances quicker. It's best to tarp the mattress and leave it long on the sides before you put on the vinyl/PVC sheets. Then tarp the floor and run a trail of it to the bathroom too. It's a lot of set-up, I know, but it's so helpful for quick and easy clean up.

That's why I'm a fan of these.
https://www.amazon.com/Passion-Lubes-Inflatable-Vinyl-Massage/dp/B00S8Q24WU

Granted, I haven't really had an opportunity to test one.

If you have a worn out air mattress those are good too just as a cover, great protection. A working air mattress holding air or slow leak is good too partially inflated makes for fun sploshing fun in the middle while sunk down there at the same time, slimey wrestling in that is especially challenging and also erotic, where one can could be dominant and keep the other pinned down in whatever goey or watery mess there is. We did this was a 1 1/2 foot tall air mattress which is deeper and harder to try climbing out the center of but fun and challenging, especially when tied up, hey that might make a good scene.

Just IMO, but $100 bucks for a single-use "fetish" mattress cover is a sucker's game - it's like shopping for craft tools at Michaels or JoAnn fabric and paying a 300% markup just because they're pink. You can get a roll of vapor barrier plastic at any hardware store that will easily supply years of coverage for a fraction of the cost, and usually with twice the thickness. IIRC, the last roll I got was something like 10' x 200' and as thick as the original plastic the mattress was shipped in. That being said, reach out to your local mattress store - they likely have lots of perfectly-sized bags they just discard when setting up their demos or their home installations.