A childhood belief about swimming pools

My mum told my sister and I that we were moving to a house with a disco in the attic and a swimming pool in the cellar...she kept this going for weeks and my sister told all her friends at school. I spent ages trying to figure out how the water would stay in the cellar and how people could swim in the dark (cellars were always dark in my childhood imagination). When mum told us it was only a joke, my sis had to tell all her friends at school! meanwhile i was still trying to figure out if it WAS possible to have a swimming pool in your cellar and worried for weeks about electricity and the dangers of filling up your cellar with water!