Grounding : Grounding is when a ship strikes the seabed unintentionally. 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 : Stranding is when the ship then remains in grounding position for some length of time. ( for a few hours or so).
Beaching : When a vessel is grounded intentionally she is said to be beached.
Ref: Funnel 2 Tunnel website