I filed the bottom corner edge of the nut off a little, so it could tighten all the way down, and ditched their rubber washer, as the hole in it is too big, causing it to squish down unevenly. I replaced it with two red fibre washers that have a correct size hole for the bolt. They stop the magnet cracking when you tighten it up, like the rubber washer is meant to do, but they don't crack & perish with age like rubber washers do. Cheers

What a fun and clear video! We hope you'll get some nice objects out of the water. Have fun!🧲