The neighbors of our cabin (listed Airbnb and VRBO) treat our back yard as their own space. They have done this for years, before we owned it (when our parents owned it) so we didn’t ever address it. The situation is that the houses are up on a cliff that leads down, about 15 feet, to a flatter place beside a river. All of the houses, up to ours, have a levee that makes the access to the river more difficult. All of our properties also go across the river and are only 50 feet wide so easy to walk across. Our place has a sandy beach, which is missing from the other properties. [Well, the place next door does have a beach but it is smaller and rockier than ours. The neighbors have, in the past, built a fire ring and a curve a rocks, burned the wood from deconstructing their place to enlarge it, stuff like that. The Lodge, just on the other side of this neighbor, also uses it - at least twice to have weddings!! About five years ago they, the next door neighbors, have turned their place into a STR, and they have learned that ‘all navigable water is the property of the people of the US and people can use the land up to the mean high water line for fishing, etc.’ Our river isn’t navigable, but it is considered so for this. Because of this, they have declared that all of our property up to the base of the cliff, is their property, or at the very least public property. So, their guests come over and use our beach and set up easy ups and chairs and coolers and stuff and leave it there. Sometimes, that causes other people to do things to our property, like cut down small trees to make room for their kids because the main part was taken up with an easy up, even when the people are not there. Keep in mind that this is on our property and not on either of theirs. The neighbors, themselves, have also chopped down some of our trees, I think just to allow their people see more of the river. One time, the only time we actually asked the guests for some space on our beach so we could walk through with a six man raft on our shoulders, they told us that the owners of their place said that we didn’t own this property and that they didn’t have to listen to us. They then lined up their chairs all the way across the beach and we had to thread our way between them. They, the owners, are very nice people to talk to, except for this thought that our property is their property. We did have a discussion on ‘how we can share the beach’, which to my way of thinking is like having someone walk up to you at lunch and discussing with you how you and they can share your sandwich. Anywho, I’m a bit worried about what will happen when our clients want to use the land that they have paid to rent but it is taken up by people who have paid to rent some other piece of property. Any suggestions?
A fence?
A survey?
202020
Exactly what Debthecat said! Are there property markers? If not, contact the township and request property markers then build a fence (if allowed) right on the property line in your backyard and post signs “no tresspassing.” Let their guest use their levee to get down to the river. It’s really a legal issue because if one of their guests gets injured in YOUR backyard, you’re liable and they will sue YOU. Blame your lawyer or your homeowner’s insurance agent if you want to keep the peace with your neighbor. Tell them you were advised by your lawyer to protect yourself from lawsuits.
Those are good suggestions. Unfortunately, a fence is not an option. When it floods (about every 50 years or so), the water can come up pretty far so, no fence allowed or wanted. I did put up signs once but the Lodge manager stole them - twice - and then called the cops on me! When I explained it to the cops, they finally said that they would talk to the guy. When I then asked them if I could put up more signs, they said, ‘Don’t expect them to stay.’ Not reassuring. I might try some signs, some classy, metal ones maybe. One thing I want them to say is, ‘Please treat our back yard how you would like complete strangers to treat your back yard.’
A letter along the lines of
We have recently changed our insurance provider, due to their terms and conditions we can no longer allow access due to liability issues
Well, what land are they referring to? The land in the river? So they can walk into the river and fish, like fly fishing in ‘The River Runs Through it’? Surely, this cannot mean that they have access to all your land adjacent to the river.
I strongly recommend you talk with a real estate attorney. One issue might be whether based on your parents’ and your prior ‘permissions’ the neighbors have acquired an easement.
You need to find out what your rights are and how to preserve them. I’m concerned that by your permitting people on the property, even taking no action when they are cutting down trees, that you could be tacitly waiving your rights, and with it a substantial value of the portion of your property – perhaps incurring legal liability for accidents as well.
I wouldn’t be surprised if your attorney drafts a letter to your neighbors stating your rights, perhaps also recommending signage on your property. You might well need to enforce whatever rights you have so your neighbors know you mean it.
Been thinking
A row of white painted stones on the property line with No Trespassing spelled out on them 
Is there any reason why you need to set expectations for your own guests that the areas in contention are private and part of what they paid for? Why not just use wording for your listing that makes it clear those areas are shared with your neighbors and their guests?
I understand the property/legality issues, but it seems that this has been going on with this beach area for years- why be contentious and fight with the neighbors? Is it really such a big deal?
If not a fence then some large shrubs or fast growing trees that would make it difficult for them to cross over onto your property.
I really wouldn’t put anything in the listing saying that the back yard is shared property as the neighbors could use that as an admission. I think that would be a big mistake without first getting a qualified attorneys advice.
I think it is a big deal because it substantially reduces the value of the back yard. What if there is a party with lots of people there? Maybe your guests cannot enjoy the back yard.
I also think that when this discussion reaches its conclusion the moderator should delete this post and all the comments as it would be ‘discoverable’ in the event of litigation and would not be in the interests of the OP.
I didn’t say they should say it is “shared property” in any legal way. I suggested they not set up expectations that it is private, i.e. that neighbors might be on the beach in front of the house or cross the yard to get there.
Rather odd how humans are always trying to teach little kids to share, but the adults are all about “mine!”
You need to get good 4k security cameras and record all activity.
Yes, you need a lawyer, and not some namby pamby real estate lawyer, but someone who deal with property DISPUTES because that’s what this is.
He needs to write a letter to all violators telling them what your rights are and that they are trespassing. If it was me, I would ask lawyer to warn them, advise that you will prosecute violations, and then do so, asking for the maximum penalty.
Once, or at the most, twice should stop it quickly, and of course you need to make sure that violators pay all costs and attorney fees.
As others said, you can use boulders to mark your boundaries.
All this is really good advice from @NordlingHouse
But in the US you usually don’t recover your legal fees unless you have an agreement that says you do. Still, the value of your property’s resale value, the value of your business, legal liability, your insurability (and increasing premium costs if one of these neighbors has an accident or creates a nuisance on your property) is AT RISK.
I’d be very concerned that neighbors will argue – IF they can get the evidence and are willing to invest in a legal suit – that they have acquired an easement to use your property. I would think that the legal fees are a business expense you could deduct taxwise in US. It might well be that the neighbors are not inclined to spend money to press their case once they SEE that you are serious. Be sure you are complying with all aspects of the law in what you’re otherwise doing (building code compliance, for example) in case they attempt some kind of retaliation.
I strongly echo @NordlingHouse 's advice to get a lawyer who deals with property disputes. This is itself a project. Getting the right lawyer is KEY.
The OP should not have ANY discussions with neighbors and certainly nothing in writing before engaging this attorney, and then strictly follow the lawyer’s advice.
Again, this whole posting should come down as soon as the moderators agree that it’s served its purpose.
If not a fence, which makes for great neighbors, then a day in court. If the neighbors are so lovely and splendid why is this hassle a reality? The last thing you want to do is play traffic cop. So you either live with it (share and take your chances) or you don’t (go to court and have a neighbor that now will hate your guts, so what if they are that inconsiderate).
So this is not related to water rights but when I purchased my home, our title survey was incorrect. We didn’t learn of the error until our sewer line collapsed and discovered it went though our neighbors yard.
The next few years I learned that:
a) you have to sue a title insurance company - they just don’t pay out on a claim.
b) that neighbors lie.
c) While they did own the land, there was an easement that allowed us the right to passover. but turned out there were other easements from the city too.
d) Finally, If the land in question is registered land, advertise possession can not be claimed, at least in my state of MA>
I’m not sure if it’s a real estate attorney is what you need but they will steer you in the right direction. For me, I did a lot o the research myself with the title searches so I saved money. Get a good lawyer and good luck.