Jon,

It's true, finding quality photographs for zilch is almost non existent. If you'd rather not spend the money, I would suggest taking your camera (or getting a disposable one), creating the scene your looking for; in this case people having a grand time at/near the pool. In fact, you can probably ask your client to take some for you from their clients (be safe and ask for a release of said pictures) or take them yourself. Get the film processed and ask for a CD and your all set.

Now, some will argue that you should just take the snaps from a digital camera, cutting out the middle man. But my personal experience is that a standard 35mm picture when processed through the big boys equipment far supercedes the dig. cameras quality. Hey, I had two of them and ended up selling them..

That's what I have been doing for the longest.

my $.02.