impluvium is the answer
The Latin word for rainwater is aqua caelestis.
reddo is latin for translate.
The rainwater will be treated by the chlorine in the pool and you may have to adjust the chlorine levels. See the related link for more information.
Filter it then swim in it.
Go to google translate select translate form English to Latin and type what you want!
The word surprise in Latin is admiratio
Odimus.
natur
Salvatus.
Movi.
In processu.
Vita.