Currently, water utilities cannot find leaks before they grow into costly pipe bursts. With Lighthouse, they can find leaks months before they break. Every day 20% of the clean water produced in the world is lost due to pipe leaks. Due to limitations in current technologies, most of the leaks are either not found, or found too late. Every year, there are 240,000 water pipe breaks in the US, and many of them cause sinkholes and other severe damage to the infrastructure. Water utilities need methods for detecting and locating such leaks before they become big breaks, so that they can perform preventative maintenance to save water and protect infrastructure. If we can find and fix half of all leaks in the world, we can recover enough leaked water to support 1 billion more people's daily need. Lighthouse is a low cost robot that can travel inside underground water pipes and proactively find leaks.