I have a long story about this, but will cut it down to medium length so as to not bore everyone.
Back in 1986, a friend told me about a lake he had come across in an area of our county that was just starting to be developed. He said it was called Oso Reservoir, that it was a small feeder lake to the (now) well known Lake Mission Viejo and that it was used to keep the Mission Viejo water level at a stable point. He told me that while Mission Viejo is a private lake, Oso was on public lands and could be fished if you had a license & were willing to make the trek to it. I bought a fishing license that day and got directions on where to park my truck & meet him there the next morning.
We parked on a public street next to some Model Homes that were being built & made the nearly mile walk through the brush. A quick climb up the earthen dam revealed a triangle shaped lake, about 3/4's of a mile long. No fencing, no signs, just a secluded little watershed tucked into the foothills. We caught about 30 bass in the 4 hours we were there, the hot July sun finally getting too much to bear. We decided to come back that evening for a few hours to finish off the day.
I arrived that late afternoon before my friend & headed off to the lake instead of waiting for him. I was fishing a spot about 100 yards down from the dam & the fish were just as willing to bite as they had been in the morning. I finally see my friend & another buddy of his crest the dam. I yell out & wave to him and as I do, suddenly there is the deafening roar directly behind me. Like a scene out of Apocolypse Now, a helicopter had flown low over the horizon, up over the hill behind me and was headed directly towards me. I look over to my friend & see him & his buddy running as fast as they can, now I have no idea what is going on. Scared out of my wits, I drop my pole and take a couple of steps back into a large bush to conceal myself. The helicopter buzzes over the top of me & then does a 180 so they are now facing me. I have no clue what is happening, so I just hunker down in the bush, not moving. After what seemed like an eternity, but was probably 15 seconds, the helicopter flew back over my head in the direction it had originally came from. I didn't move, instead just listened & noticed that while I could still hear the helicopter blades behind me, they were slowing down. I crept out of the bush, peered back behind me to see that the helicopter had landed on the shoreline. Just as I realized it was a police copter, I see a sheriff approaching me from the side, hand on his weapon & EXTREMELY ticked off.
By this time, I am freaking out. I knew this cop was livid and I had to do something to calm him down. I put my hands in the air as he approached me and he continued to yell at me 'What the hell are you doing?" For a reason that to this day I can't explain, I tapped my hands on my ears, made some phony sign-language signs and mumbled some nonsensical sounds. The sheriff stopped, looked at me oddly and said "What?". I repeated the gestures. The sheriff asked "Are you deaf?", to which I nodded yes (I must be a superb lip reader). He immediately calmed down, took his hand off his weapon & said "Oh, Ok." He pointed at my tackle box & rod and said slowly "Pick...up...your...gear..........You...are...under...arrest". I nodded again and as I gather my stuff, he pointed for me to walk up to the dam, where I saw a sheriff's cruiser parked with another cop talking to my friend & his buddy. I found out later there was a fire access road about 2 miles to the north that led to the dam, something we never saw but that was used by the sheriff to patrol the area.
Turns out this was not public land, but rather land owned by the developer of the model homes we had parked by. The cops put us all in the cruiser, took us back & around to where we had parked and ended up writing citations for trespassing. By this time, I had given up the deaf routine and the other sheriff had no idea what I had done earlier. We were able to keep our gear, but were looking at a fine in that could reach $100 (in 1986 dollars).
That evening, as I told my fiancé the story, I started to get a little uppity about the situation. After all, no fencing, no signs, how were we supposed to know it was private property? After a few hours of playing Perry Mason in my mind, I made the decision to return to Oso the next day, this time armed with a camera instead of fishing gear. I was going to build a bulletproof case to get out of the trespassing fine.
My fiancé went with me the following afternoon (a Sunday). I again parked next to the model homes, and told her to stay with my truck. I walked towards the dam, taking pictures along the way to show a lack of fencing or signage. As I get to the base of the dam, a security officer from the developer comes driving down the service road. I wait for him & when he pulls up, I show him the previous days citation and explain what I am doing. He says fine, but that I need to get into the truck so that he can escort me to the dam for the remaining pictures. We get to the top of the dam, he tells me I can get out to take the pictures I need & that he has to drive to the other end of the dam in order to turn around. When he comes back, I get back in his truck & he says "I went down to the other side of the dam to call the police (-this was before cell phones-). You knew you shouldn't have been here, so I had to report it. When the police get here, they will decide what to do". That was fine by me, I figured I could explain my situation & all would go well. He drove around the service road exit and then back over to where my fiancé was waiting. We all chatted, waiting for the sheriff to arrive. 10 minutes later, the sheriff shows up, pulls the security guide aside to talk with him for a few moments and then approaches me. Just as I get ready to start explaining myself, the sheriff says "Put your hands behind your back". I do as he says, but respond incredulously "You have got to be kidding!". As he handcuffs me, he says "I don't kid about this". A few minutes later, I am being taken down to Santa Ana county jail, where I was booked & then released on my own recognizance.
Turns out the sheriff told the security guy that it was up to him what the sheriff would do, either warn me or arrest me. The security guard told him to arrest me, which he probably later regretted as my sweet, innocent fiancé freaked out and started dropping F Bombs at him for doing that (after the sheriff left).
Without getting into anymore lengthy details, I ended up pleading my case when my hearing came up, using the pictures I had taken and the fact that I had bought a fishing license the day prior (showing that I was under the impression that it was a legal place to fish). Both the arrest & fine for me were dropped, but my buddy & his friend ended up having to pay about 35 bucks for their tickets (no fishing license). A couple of years later, the developer entered into an agreement with a private party to allow Oso to be fished as a private lake in exchange for waving of all liability and for the private party to provide security. If I am correct, lake access is now under control of the Boyscouts.
Ironic thing is that where I live now is about 3 miles away from the lake and a toll road goes right over that same dam, so I see the lake on a near daily basis.