I can only sympathise with the original post. There is a council owned pond where I live and it is open to the general public.
However every Saturday morning a large group of model yacht racers turn up and take over.
They will stay at the pond until the sun goes down and beware if you get in the way.
I have seen them telling young children, paddleing in the water, to get out as they are distracting them from racing.
Not only that they patrol the course in a little inflatable with an electric motor to deter people in canoes etc from
getting too near the course.
I have approached them on several occasions about sailing my model on the pond, being polite about frequencys etc, to be told that all the channels are allocated for the day. My model is not a yacht.
So after complaining to the council and being informed that the yacht group have no rights to pond time etc, I tried again to get my model in the water, but all in vain.
The next step was a bit drastic, I would go up every Saturday morning and take my transmitter with me.

Sitting in the car I would wait until they started a race and switch on my transmitter, not touching it at first i would then push and pull the levers until I could distinguish what yacht was on the same frequency.
It was just a case of waiting until the first turn of the race and yes I would turn my adopted yacht into the rest of the group.
Chaos was the normal result, with the offending skipper getting a mouthful from his friends.

After an hour or so and different crystals I would turn the transmitter off and go home happy, it was just as good as sailing, even though it was someone elses yacht.
And yes they still sail there to this day with total disregard for any other user of the pond.