It's no more than symbolic, firstly Osama hadn't effectively been al-Qaeda's leader for years, secondly al-Qaeda itself is largely a non-factor anymore it. It likely doesn't have the power to actually launch large-scale terrorist attacks anymore.
Not the way it was done originally, they'd be wrapped up (usuaully just a blanket) put some weights inside and just dropped into the ocean, mostly done (obviously) for sailors who had died at sea.
