The Speedo is a custom item on the Civ+ Minecraft Server. It is a pair of leather pants that increases the swimming speed of the player while in water, making it similar to using a boat.
The Speedo was added as a way to improve the experience of swimming in water on the 1.8.9 version of the game. Boats on this version are generally unpleasant to use, so the Speedo provides an alternative way to quickly move through water.
Players can obtain the Speedo by crafting it using leather and lapis lazuli. They will also receive it in their inventory when they first join the server. Once equipped, the Speedo will automatically increase the player's swimming speed while in water. This can be useful for exploring underwater areas or quickly crossing large bodies of water.