Instrumenting a lake as a wide-field gamma-ray detector

Ground-level particle detection has recently emerged as an extremely powerful approach to TeV-PeV gamma-ray astronomy. The most successful observatories of this type, HAWC and LHAASO, utilize water-Cherenkov based detector units, housed in tanks or buildings. Here we explore the possibility of deploying water-Cherenkov detector units directly in to a natural or artificial lake. Possible advantages include reduced cost and improved performance due to better shielding. The lake concept has been developed as an option for the future Southern Wide-view Gamma-ray Observatory, and is now under consideration for a possible future extension of the observatory, beyond its recently selected land site. We present results from prototypes operated in a custom built facility, and concepts for full-scale array deployment and long-term operation.