I don't know. What I am asking is:
What law governs abandoned stuff?
What law was broken?
Abandoned or not, I do not believe you can legally destroy something that is not yours. The Florida theft statute is pretty comprehensive, basically taking of possession of anything that you know not to belong to you is theft.
And if destroying abandoned stuff was for the good of the turtles, how did it help to destroy it and leave the stuff in place, the turtle knows no difference between a float with air and a flat float.