Raw water column data were collected using the ship's own Kongsberg EM 122 multibeam echosounder during the RV SONNE cruise SO306 CoWIO. The cruise took place between 2024-08-08 and 2024-09-09 (Port Louis, Mauritius - Durban, South Africa). The primary goal was to search for cold-water coral mounds in the West Indian Ocean. Data were recorded in the EEZ of Tanzania. These studies were endorsed as an UN Ocean Decade 2021-2030 of Ocean Science for Sustainable Development activity. Data are unprocessed and therefore contain incorrect depth measurements (artifacts). Sound velocity profiles (SVP) were collected in all the main working areas and are part of this dataset.