SpaceX's drone ships have a vehicle that drives under a booster after landing and then clamps onto it to secure it. Photos of it suggest that it has neither ballast nor any way to clamp onto the drone ship.
So how heavy is it, compared to a landed and thus low-on-fuel booster? How heavy would it have to be to stay fairly motionless despite wind loads, deck tilting, and ship maneuvers?
(Here's a detailed history of the Octagrabbers.)