The Shiny Red Balloon is an accessory that increases the player's jump height by 2/3, from 6 blocks (12 feet) to 10 blocks (20 feet). The Shiny Red Balloon is found in chests in buildings on Floating Islands. This item utilizes its maximum potential when used in conjunction with Cloud in a Bottle, and vice-versa, since the second jump is affected by the item as well, increasing the double jump height of Cloud in a Bottle from 3.5 blocks (7 feet) to 7 blocks (14 feet), for a total of 35 blocks (70 feet) of jump height.
When used in conjunction with Cloud in a Bottle and Rocket Boots, it is possible to elevate to a sufficient enough height to die from fall damage. It would be wise (if this combination of items is used) to either carry a Lucky Horseshoe or a Grappling Hook to be able to negate fall damage. It is also worth noting that the Shiny Red Balloon decreases jump height in water by one block (2 feet).