Treasure Fleets is a social policy in Civilization V. It is part of the Exploration tree and requires Merchant Navy. When the amount of wealth transported by sea becomes too great and too tempting for pirates and the like, the best strategy is to combine the different merchant ships into single, well-protected treasure fleets. Similar to the land-based wagon trains, these fleets consist of many cargo ships which transport not only goods and gold, but also the provisions needed for long trips, and the mariners needed to defend them against those with evil intentions. These treasure fleets are then much more effective at long-distance trading than single cargo ships that are usually deployed by non-seafaring nations.