Hyperspectral reflectance was measured in a laboratory after collecting a water sample from Lake Bante in Wilhelmshaven, Germany during a Nodularia spumigena bloom event on 16 August 2021. A hyperspectral Spectral Evolution (SEV) SR-3501 spectroradiometer covering the wavelength range 280 nm to 2500 nm was operated in reflectance mode with an 8° field-of-view lens fitted. Each measurement was generated as the mean of 30 scans and white referencing was completed over a 20 × 20 cm SphereOptics Zenith Polymer® SG3120 ≈ 99 % full material PTFE diffuse standard panel. An Arrilite Plus 575 W high performance halogen lamp placed at a viewing angle of 45° was placed 0.30 m above the target water sample to provide a uniform light source in a dark calibration laboratory.