We put a 10' wide 30 yard long shelf in our new pond at 5 1/2'-6' deep in one corner and are shooting pea gravel over it. Should make a good spawning area and at that depth cattails should not ever be a problem.
Anything you put in a pond that can/could float you should anchor, also keeps it from ever moving. I like to use cinder blocks even new ones are cheap tied with stainless steel wire so it won’t rust or break.