A prototype point-source integrating cavity absorption meter (PSICAM) is presented and compared with spectrophotometric absorption measurements. Different light collector assemblies of the PSICAM were tested regarding their capability to determine the absorption of water constituents accurately over a wide range of concentrations and scattering properties. The PSICAM setup with a radiance-type sensor showed the best performance. It was compared with a photometric absorption determination using nonscattering dye solutions. The mean difference between both methods was less than 2.4% in the spectral range of 400-700 nm. The absorption determination with the PSICAM, when equipped with a radiance sensor as a light collector, was only little affected by scattering and temperature. We conclude that the PSICAM can be used to determine the absorption of natural seawater samples at ambient temperatures.