I've masturbate in so many various places that don't feel particularly unusual. For a couple of years I my job required a lot of traveling by car keeping me gone 3-4 nights every week. I was 22 and always horny. Back then we didn't have car stereos and AM radio sucked in the rural areas I'd drive through so I had a lot of bored time. Quite often I would pull out my dick and just play with it while driving usually trying not to ejaculate until I got to my motel room for the night. Several time a semi driver would get an eyeful as we passed each other and give a quick toot of his horn in appreciation. One time when my girlfriend (now my wife) were driving back east from Oregon, somewhere in South Dakota I felt extremely horny and wanked while she slept in the seat next to me.
I love masturbating outside, in the woods, in my back yard, on the trails, etc and have never been caught though my wife and I have been caught a couple of times fucking along a trail somewhere.
As a teen, I often used to masturbate in the back seat at night on a long trip. I could do it quietly and would stuff a tissue down my pants to catch the cum. As far as I know nobody ever knew.
Hot tubs! Many times I'd let the jets massage my cock til I'd have a strong orgasm.
One night on a red eye when I had no seatmates I had a long slow session with a blanket over my lap.
The only time I ever got caught was one night when I was in our dark bedroom watching the lesbian couple next door having sex. I had dropped my pants and was standing wanking when she walked in. She was a bit pissed but fucked me later that night.
A few years ago I had two days off each week in the middle of the week over the summer months. I would sun tan nude and surf here while out on the back patio. The patio is private and safe from the neighbors. I don't close the blinds in the back of the house as no one is home while I am naked outside on the patio. What I didn't remember was the girl friends mother had a key! Caught nude yes. Caught masturbating, I don't know. She called my phone to ask if I was home. I said yes and ran my naked ass into the house as she said she was at the door. I didn't know she meant was inside the house at the patio door. I didn't even have a towel.