Trespassers on lake

We are one of three HOAs in Florida that share the use of a common lake for boating and recreation. One third of the lake is owned by one HOA, one third by our HOA and the remaining third is in a Trust. The problem is that a group of rowdy, noisy teenages who use loud vulgar language are swimming in the lake in order to get to an island with a beach that has been long used by homeowners and their children. They leave piles of trash behind and intimidate the homeowners. There have already been several altercations but no one has been hurt (yet). The teenagers are entering the lake in the portion that is in a Trust and swimming to the island (also in the Trust).
I am on the architectural comittee and the Fining Comittee and have suggested we erect a "Private Property No Trespassing" sign where they are entering the lake. The Board says we can't erect a sign nor prevent the teenagers from going to the island. By the way, there is also an alligator that lives close to where they cross.
We are concerned not only for their safety but also for the peace and tranquility we no longer enjoy. Can we legally erect the sign? If someone is hurt (drowned/eaten) who is liable? The HOA or the Trust?

JohnB

If I read it correctly, the OP said that the part of the lake used by the kids to get to the island and the island itself are in the name of a trust. Neither is the association's property. I do not believe the association can call the police about trespassing if not their property.

If I have it right, then the association members are trespassing on the trust's property as much as the kids are.

Now feeling threatened by and objecting to the foul language of the kids while we are all on the island is another issue. If I felt threatened, I would call the police no matter where I am.

Hope this helps.

I agree with both Johns but I would also consider erecting a "no trespassing" sign on the HOA property as well as a "swim at your own risk" sign, with maybe the phone number for animal control. That would maybe help homeowners feel empowered to call on these trespassers as well as be prepared for any gator mishaps.

We had a similar issue. The lake where I live is large, and there we couldn't prove the teenagers used our property to access the water and islands. We had luck with calling the police about their behavior and language (using profanity, threatening others etc is a crime here) - the police couldn't help us with trespassing but they were happy to help us with that. Hasn't been a problem in over a year.