If you click through to the NYPost article, it mentions that he didn't have any ID or anything on him:

  “All his IDs, his money, his car keys — they’re all gone.
  They sunk with the jet ski,” Cowan said.

I can see them initially arresting him for trespass, but after the matter is sorted out, I would expect them to drop the charges. If they keep pushing for them, it doesn't make any sense (other than in a "you embarrassed us, and now you'll pay" sort of way).