Small urban waterbodies (SUWs), such as stormwater management (SWM) ponds and wastewater lagoons, are essential assets for municipalities because they control stormwater, treat wastewater, and build climate resiliency. However, as global efforts to quantify greenhouse gas (GHG) emissions intensify, SUWs have been identified as potential sources of methane (CH4), although quantification methods vary. A static, closed flux chamber with real-time sensors was proposed as an alternative to traditional methods of syringe sampling and GHG analyzers to reduce atmospheric contamination during sampling and improve spatial variance testing at a lower cost, respectively. A floating flux chamber was designed and constructed using 3D-printed materials and hardware store items for ~$1,150 CAD. It was calibrated and validated in a laboratory by injecting known quantities of gas into the chamber and comparing recorded concentrations with samples analyzed using gas chromatography (GC). Validation experiments showed that the sensor reported 95.9% (R^2 = 0.9987) of the values the GC measured. The system was deployed in a wastewater lagoon in Almonte, Ontario to provide proof of concept and calculate flux in a real SUW. Equilibrium was reached quickly between the chamber gases and the water, as evident by a large increase in concentration followed by it approaching an asymptote. Apparent areas of higher emissions produced fluxes of 254 ± 42 mg m-2 min-1 by exponential fit and 244 ± 19 mg m-2 min-1 by linear fit. Additional field tests will be performed in Spring 2026 to determine how emissions vary spatially across SWM ponds.