I agree with the advice on having a method of cutting the anchor line, but do not particularly like a sharp pointed knife around my pontoon. If you can figure out where to buy one or two of these film cutter they would appear to be excellent for that purpose unless you are using some serious line for your anchor. I could sell you a box of 100 but not just one, I'm afraid that's a problem with finding it. They are about half a dollar and designed for warehouse work cutting plastic wrap off cartons.
Plastic wrap cutter.JPG