You would need to post at the four corners of your property with signs stating "No Trespassing" in letters at least 2" high and also listing the owner of the property. There must also be signs no farther apart than 500'. The signs must be prominent and visible from outside the property. Then, if someone is trespassing a law enforcement officer can charge them with violating Florida Statute 810.09, a first degree misdemeanor. If they want to claim a right to pass over your land because their land is land-locked they will need to take some legal action to secure that right. They cannot merely trespass.

You could also bring a civil tort action for trespass, but you'd have to be able to show damages to get more than $1.