Beaching : It is the act of INTENTIONALLY GROUNDING the damaged ship in order to save it from sinking.

Grounding : grounding occurs when the a ship touches bottom accidentally. This act is not intentional. It occurs generally through poor navigation and the lack of underkeel clearance. The severity of any damage incurred will depend on the speed of striking and
the nature of the ground that the vessel contacts

Stranding : When a vessel has been grounded for a period of time it is said to be stranded for the purpose of Marine Insurance.