I've been caught three times :

1. In my mid twenties I lived in Teesside ( North East England ) while there I found a small wooded area with a old silted up creak bed, the mud there was around 4ft deep and one afternoon in just a pair of trunks I wandered down and enjoyed myself for around an hour before submerging deep into the mud. A few minutes went by and two teenagers turned up they were clearly bored and started throwing stick and small stones in the the mud, It wasn't until half a house brick landed inches away from my head did decide to stand up! I must of swallowed either some mud or water and coughed to clear my throat while the teenagers weren't looking. They turned to see a 6ft mud covered figure in the bog pointing at them, scared they screamed and ran off - I quickly jumped in the stream and got washed and left before they came back.

2. 2014 I was living in Lancaster ( North West England ) after a week of work I just needed to relax and went out walking, it was there I found this old semi overgrown wooden jetty that went out towards a silted up muddy area just off the main river, the mud was so soft and sticky oh it was heaven around 5ft deep and you could swim through it like being in cream. Well my third of fourth visit there I stripped down to a pair of swimming trunks and bagged my clothes and stored them under the jetty and slipped into the mud, around twenty minutes later I heard someone coming down the jetty so with a deep breath I went under - I waited and then slowly came up, I wasn't fully visitable but my eyes met this dog looking down at me, standing next to the dog was this middle aged woman smoking a cigarette. The dog made this noise and the women looked at the dog then her eyes caught mine! she froze staring at my eyes. As I took a breath in and slipped under the mud again and slipped under the jetty she didn't see or notice me and while I waited for her to leave I got out and quickly got washed in a near by farm water feeding tank. I later heard she came back with someone and found foot prints but nothing else.

3. More recently I now live in Rural North Lincolnshire, there's a near by construction site of houses being made near a muddy patch of ground - I wasn't expecting anyone to be there on a Sunday as I put my red tracksuit on and slipped into the mud! wet but sloppy it was heaven I just went under and held my breath and as I came up I felt water hitting the top of my head then on my face, as I opened my eyes there stood a guy in his mid 40's urinating he looked stocked as did I, no sooner had he stopped and zipped up turned and walked off I got out and left.

AMAZING! Mud AND urine???

I've been caught a few times, usually from people curious as to why this weirdo is up to his waist in mud, fully clothed.

Only once have I been freaked out when I've been caught by, how shall I put it - people in charge of law and order...

Never went back there again...

Caught [by other people] in mud? .... no, that is one of my mortal fears! lol.

Though, I've had a few strange encounters over the years. For perspective, I live in an area with an average of ~36 people per square mile. So once you get outside a city, you're pretty unlikely to actually run into anyone else. But on 2-3 occasions over the past decade or so, have run into people.

As an example, just a few months ago I drove out to a parking spot for the ~3/4 mile hike into a mud spot I like. In the past ~10 years I've only ever encountered one person at this parking spot. But this time, I pull in, and ~30 seconds later - another truck pulls in. Not wanting to seem weird, I say 'hi' and start a friendly chat. I guess they had trapped a racoon in their garden and drove out to the country to release it. So here we are! Both at the same spot. Luckily, they release the critter, then take off. I load up my gear and begin my hike to the mud in peace!

My main worry is that we'd be chatting and I'd mention, "Oh, just going on a hike." and they'd think that was a wonderful idea and want to come along. Then it would really be "just a hike"

Kind of, but as part of my second job so nothing meant to be sexual in any way, basically I had to enter hippo filled water to free a hippo that got stuck (can't remember how it got stuck) in the pond of its habitat (zoo not wild to be clear) anyway I went into the water before opening time with a team providing safety cover from the shore, however I ummm lost my wetsuit during the rescue after it got stuck in the mud and ripped open (by the shovel I was using) and dragged off me by the mud as result forcing me to swim fast through the water into the hippo house to what should have been privacy apart from a female colleague who was the internal safety cover, however as I stood up to get a towel around me and was left of my swimwear I had worn underneath the wetsuit, the zoo senior management team walked into the viewing gallery that was still closed, so there was me wearing a towel and bikini bottoms up to my thighs in muddy, stinky, sh*tty water that hadn't been cleaned out for two days (partially to simulate the natural environment the pond was only cleaned out once or twice a week, the other reason being a safety matter, to clean out the pond the on-site ZERT were needed to provide safety cover)!

Years ago while biking, I found a dried up creek that was only deep creamy mud. I couldn't resist taking my shoes off and wading barefoot above my knees.
Then I turned around and saw a guy in a construction vest just staring at me, so I quickly got out and biked away. He must've thought I was some sort of weirdo.

Yeah, I've been 'caught' a few times..... The worst was when my folks came home unexpectedly, and I had gotten muddy in our backyard. I wore white under-pants back then, ( I was only around 10 !!! ), not sure what I did with my other clothes, jeans, boots......, but I had left my under-pants soakin' in the bathroom sink as they had gotten muddy. We had a small house, with only one full-bath... Can't believe I forgot about my underpants....
My Mom found 'em in the sink and came into my bedroom to ask about 'em. I lied to her, said I had had an 'accident'...., but she came back a few minutes later and said my under-pants were muddy, not the other thing...., and I had to lie to her again, tellin' her that I had gone out with friends earlier and gotten a little muddy....

It was an awful experience, and I felt terrible. I had no idea what my Mom thought....... Though a few years later, I came home all muddy, (didn't expect her to be there....), and said I had fallen through the ice while skating, (it was Winter...). And I got 'royal-treatment !!! She told me to take a hot bath, washed my clothes and made me hot-chocolate !!!

Other times I've been 'caught', but as long as I'm not 'jerkin-off' with my 'boned-up' cock stickin' outta' my pants, it's really not a big deal... So what, I'm all muddy !!! Some strange looks, but who cares......

Once I visited a quarry near where I live. it used to have these pools of thick smooth orange clay that was like smooth peanut butter. I went there one day when the site was closed, and made sure nobody was about. One of the settling pools was right next to a public footpath that ran through the site, I hoped over the short railing that separated the path from the pools, I took off my shoes and waded barefoot into the mud and was stomping around in it for a good 15 minutes.
Before I could even react, the guy ran past on a jog. he slowed down adn gave me such a confused look before carrying on with his run. I decided that was a good cue to leave, so got out of the mud and tried to clean up the best i could. I looked around and noticed the guy had got up to an embankment around the far end of the pool, and was stood watching me. I got out of there pretty quick after that.

funnily enough, at the same site I came across 2 wammers that used to post a lot of this site. they weren't muddy, but I could tell they were planning to film a scene in the quarry mud. I was so afraid to say hi at the time.

Would have been all too funny if you could have ended it with... "But looking back, there wasn't any active construction within 10 miles of the place." Then who would be the weirdo!