No, it is not safe, my advice is DITCH IT.

I have been riding for over 3 years now (not saying that is long) and have NEVER lost a board. The reason is because body dragging is easy and even while falling or getting dragged I am making note of my board's location.

If you are concerned about loosing your board in the gulf, use a gojo (is that what it's called? I can't remember) instead of a leash. Could save your life or at a minimum your teeth!

Write your name and phone # on your board.