The report demonstrates how the hydrooptical environment affects the performance of a depth sounding lidar system. Results from a literature search of databases of optical transmission data (through satellite and in-situ instruments) from Swedish and international waters are presented. Information from the databases can be used for performance estimation of underwater optical systems. The results can be completed for implementation in tactical support tools. A four-year optical transmission measurement campaign in the Stockholm archipelago is presented and seasonal variations of the underwater optical attenuation are described. We also describe a simplified model for depth sounding lidar system performance estimation. The depth sounding lidar can be used for environmental assessment in littoral zones and for search operations or detection of shallow underwater targets such as mines or AUV:s. The purpose of the simplified model is to estimate the signal level and maximum depth range for different targets, bottom depths and system parameters for various water types in international and Swedish geographical areas.