A more thorough explanation:

Accidental stranding is a term used in maritime law to describe a ship that has drifted, driven, or run aground on a strand due to natural forces such as wind and waves. This is different from voluntary stranding, which occurs when a ship is intentionally run ashore to avoid a more dangerous fate or for fraudulent purposes.

When a ship is accidentally stranded, the liability for any resulting losses is determined by the type of stranding that occurs. If the ship and cargo are exposed to a common peril by the accidental stranding, the expenses of unloading and taking care of the cargo, rescuing the vessel, reloading the cargo, and other expenses other than repairs requisite to enable the vessel to proceed on the voyage, are brought into general average, provided the vessel and cargo were saved by the same series of measures during the continuance of the common peril which created the joint necessity for the expenses.

For example, if a ship is stranded on a beach due to a storm, and the crew must unload the cargo to prevent it from being damaged, the cost of unloading and taking care of the cargo would be considered a general average expense. However, if the ship is intentionally run aground due to negligence or unseaworthiness, the ship cannot claim contribution for any resulting losses.