Image imported from derpibooru
Original Description:

Parade balloons are naturally pretty light things, so finding fitting pools for them can be a difficulty, especially when water is so dense and pushes back against them so forcefully. Luckily, for those few parade balloons that don’t mind filling themselves up with air for awhile, there are other fluid options - for example, extremely dense gases instead!

Here we find Emilia enjoying just that, with some appropriately-sized water wings and puffy padding to help, a bouncy castle makes for an airtight enough enclosure for holding a veritable swimming pool’s worth of gaseous P-235~ Despite its common decay product of Helium, P-235 itself is an extremely dense gas - each individual atom producing hundreds of atoms of P-235, it’s quite easy for light things like pooltoys and other inflatables to float ontop of its surface, while not being too squeezed if they want to sink their hooves in a bit deeper. Perfect for a relaxing evening, and all the more fun if a non-pooltoy friend decides to come along and get tugged inside to join the puffiness~

Commission for Emilia Starsong~