Don't clip it to some ring somewhere and let it dangle. Get one that fits in a pocket.
They're a PITA.
Time spent working out some additional hand signals with your buddy will be time well spent.
Still, for some things, slates are necessary. Pop-point pencils work well when your wooden pencil dissolves. Some use disposable mechanical pencils - they go south quick in ocean, last a bit longer in fresh water. Wet-notes work well.
The less you have to use them, the happier you'll be.
To get stubborn marks off (all your gear, not just slates), use 'bartenders friend' and a green scrubbie.