Swarm intelligence is the collective emergent behavior of decentralised, self-organising systems that typically consist of a population of simple agents interacting locally with one another and with their environment. While many roboticists have explored swarm behaviors in large groups of robots, our interest is primarily in small swarms (we prefer to call them “teams”) of underwater robots. To explore emergent behavior principles, we need several (10-20) underwater robots. Although the seafaring STARFISH AUVs could conceptually be used for this study, building and operating such a large number of AUVs is challenging. We therefore developed a number of very simple low-cost underwater robots (called “SwarmBots”) for lake testing. With these robots, we were not only able to demonstrate emergent behaviors, but also take advantage of these to achieve tasks such as acoustic localization using extremely simple underwater robots.