Multibeam sonar has emerged as a powerful tool for environmental monitoring of marine renewable energy (MRE) devices. Moving away from manned operations, self-contained multibeam sonar systems may be costly at purchase, but are cost- effective for long-duration, autonomous deployments. However, there is no single multibeam sonar configuration that suits all environments and MRE devices currently being tested, and licence requirements may vary between regulatory bodies. A novel, quarter-scale tidal turbine, Deep Green (the 'kite'), is being tested in a tidal channel in Strangford Lough, Northern Ireland, UK. The kite consists of a wing with a turbine, 'flies' in a figure-eight shape trajectory underwater and is tethered to the seabed. Strangford Lough is a Special Area of Conservation (SAC) for harbour seals and a multibeam sonar configuration is required that allows the detection and tracking of seals and other marine life with high spatial and temporal resolution. Developed through a collaboration between the research team, local regulatory authority, kite developer and the sonar manufacturers, we describe the transition from a marine mammal detection system through to a configuration that eventually aims to understand the four-dimensional animal movement and interactions as well as underlying hydrodynamic features around the kite.