My neighbour - four down - built a large entertainment area including BBQ's etc. He had a fibreglass pool put in.
Decided one day to empty it out and give it a really good clean.
He went out next day and found his pool had popped up about 12" out of the ground pulling up all the pathway and pool plumbing. An idependant inspector found that they had not placed the foundations in correctly.
The pool company had gone bad and bankrupt. They openned over the other side of town under another name and are still trading - hard to prove anything there though..
Builders and pool companies - a law unto themselves sometimes!!