Today, as a water economist, my job is to help customers stretch their limited water resources. This means managing supplies wisely and getting a handle on collective demands. Fortunately, one of our available tools is an old one: water markets that can help reallocate the resource to the places it’s needed most. I’ve learned a lot more about water and water markets since I was a second-grader determined to help fish in the San Francisco Bay. One lesson is that even well-intentioned water markets can have bad outcomes if poorly designed or executed, as was my first water transfer.