I believe St. John the Baptist baptized people in the Jordan, which is bigger than a pool...
I remember coverage of this archeological find on the evening news a few months ago. They found a structure built into the rocks which they believed held a baptismal pool used by early Christians. It was in the general area of where John the Baptist was said to have preached, so there was a connection with him. Unfortunately, these stories pop up and then you can't find them when you need 'em.
Much, much bigger!