The Marine Republic was published twice by Spence at an interval of twenty years: first in Pigs' Meat in 1794, and secondly in the Giant Killer in 1814. In both cases the story is split into two parts.
The first part is largely the same in both versions, and is a development of the story of Crusonia. This time the island is discovered not by Crusoe but by a family of ship-owners who run their ship on Spensonian principles. This is the only example in Spence's writings of his Plan being applied outside farming: the ship is owned jointly, and profits are split equally among the crew, regardless of rank, at the end of each voyage. Once on the island, the sailors apply the familiar principles to the land itself.
The second part is a dialogue between a later discoverer of the island and one of the Spensonian inhabitants. However, the dialogue is quite different in the two versions; the earlier version is mostly concerned with how the Spensonians avoid reverting to a landlord based system, through secret ballots and a volunteer army; the later one with the workings of the system and the avoidance of military dictatorship (oddly borrowing a device from the story of the Mercolians, which did not originate with Spence).
- The Marine Republic, 1794 version
- The Marine Republic, 1814 version