Caesium in a swimming pool?
Now if you know about the alkaline metals, lithium, sodium, potassium, rubidium, caesium and francium, you would know the further down the more reactive. Especially the acidic non-metals, fluorine, chlorine, bromine, iodine, astatine and element 117. They also react with water to make somthing like sodium hydroxide and hydrogen. Now a swimming pool has water and chlorine which, with caesium, would react very strongly especially if it's a massive brick of it! So it would make a
BIG ELECTRICAL BANG!!!
And, since it's electrical, wouldn't it power up something like a toaster or a microwave?