boy that is a new one for me. Mud Wrestling pits? I guess you go for the female wrestlers for their diamond rings.
Or sand wrestle pits (like they have at military base PT course training fields).
But as far as mud-wrestle pits, this has sometimes been a part of triathlon competition course (one of many stations) that are gimmicky events. Yeah yeah, I know, very rare for anyone to put forth such an event.
But there was an event near me at a place called Casa De Fruta (near Gilroy, CA) that had an annual outdoor festival with all sorts of promotional festivities, games, competitions, etc... One of which where they made a temporary giant mud pit, by stacking hay bales in a giant square enclosure. Then filling the center with dirt and water to make a contained giant mud pit. Then dozens of contestant enter (yes, in their bathing suits) to frolic and thrash about.
I got a call the help with a lost ring there , after one years' event was over. The bails had been removed, and the mud was left to dry out and be disposed of. And I was asked to scan through all the dried out mud (which had been bulldozed out to the sides the week before). And I found other personal nick nacks during the process (earrings, etc....) And when an employee saw me there, he came over to ask what I was doing. After I explained, he commented that EVERY SINGLE YEAR, without exception, he hears of many such stories where some poor sap soul is out there later that night, feeling through the mud goop "looking for this or that". So apparently my singular posse ring hunt was a normal issue for mud wrestle pits.
Same for hot spring bathing : If you're in a part of the USA where there's mineral bath hot springs, those too are places where rings get lost.