The Cloud in a Balloon is an accessory that combines the functionality of the Cloud in a Bottle and the Shiny Red Balloon. It boosts jump height by 33%, and jump speed by 30%, increasing the player's first jump's height to 10.5 blocks (~75% increase), and provides a double jump that hits 9 blocks, for a total height of 19.5 blocks.
Jump height is oddly reduced when underwater, reducing your total underwater height from 15 blocks (8 + 7 from Cloud jump) to 13 blocks (7 + 6 from Cloud jump).
The Cloud in a Balloon can stack with separate double-jump items, such as the Sandstorm in a Balloon and Fart in a Jar. Stacking multiple items that give the same type of double-jump (in this case, Cloud) will not increase the effects of the jump.
Stackability of jump-enhancing accessories
Items that are in the same row will not stack in regard to the respective effect.