These 12mm diameter cork balls are usually used by Carp anglers to get their boilies to float but they are excellent as a bait float for sea fishing - its a trick I sussed out over 30 years ago.
They can be added to the snood as you would bait, add or remove these floats to get the correct buoyancy and get the bait moving and away from the crabs. Being a natural colour they are generally ignored by the fish and can be removed and re-used.
One or two of them is usually enough to get a bait up away from the crabs (one in front of a frozen sandeel really works) and they are biodegradable if they come off, which they rarely do. Use them behind a bait stop to prevent them sliding towards the rig body on a paternoster.
Pack of 100 x 12mm