A more thorough explanation:

A sea reeve was an officer who was appointed to watch the shore and enforce a lord's maritime rights. These rights included the right to wreckage, which meant that any goods that washed up on the shore belonged to the lord.

For example, if a ship sank off the coast and its cargo washed up on the shore, the sea reeve would be responsible for making sure that the lord received his share of the goods. The sea reeve would also be responsible for preventing anyone else from taking the goods.

The term "sea reeve" is not commonly used today, but it was an important position in medieval times when lords had significant maritime rights.