The lighthouses appear to be abandoned coastal watch towers that had been neglected for an unknown amount of time; at night, however, the beacon will still activate automatically. The player is able to explore the entirety of the structure, including the beacon room. It is currently unknown if the lighthouse contains any useful supplies.
As it is an unofficial addition to the game, the lighthouse can only be spawned through modding. Whether it will officially be implemented in the game has yet to be announced. Should it be added to the game, it is speculated that lighthouses will spawn in a similar manner to sea forts.