MBES bathymetry data were collected using the ship's own Kongsberg EM 122 multibeam echosounder during the RV SONNE cruise SO306 CoWIO (Port Louis, Mauritius - Durban, South Africa). The primary goal of the cruise was to search for cold-water coral mounds in the West Indian Ocean. Data were recorded in the EEZs of Mayotte, Tanzania, Mozambique, and South Africa. These studies were endorsed as an UN Ocean Decade 2021-2030 of Ocean Science for Sustainable Development activity. This dataset includes 4 bathymetric grids produced based on the MBES data collected in the EEZ of South Africa between 2024-09-04 and 2024-09-07. The grids represent 4 surveyed areas: 1) transit NS to the working area; 2) main working area off the uThukela Marine Protected Area; 3) transit WE; 4) working area in the deeper waters. Study areas were chosen based on the previous reports of potential cold-water coral (CWC) mounds off the uThukela MPA. However, the survey coverage was impacted by the strong Agulhas Current. Postprocessing of raw .all files was performed onboard by Evgenia Bazhenova and Alissa Bach using the QPS Qimera software. Data quality control included 1) verification that the SVP data were applied correctly based on the time and location; 2) blocking outer beams and in-turn data to ensure the best possible quality of the overlapping swaths, 3) manual point cloud cleaning if required. Transit grid in the north was additionally cleaned by Yukari Asakura using the MB-System software http://www.mbari.org/products/research-software/mb-system. Depths measured by the MBES are reported in respect to the water level. Only static draft was taken into account. No tidal corrections were applied during the data acquisition or data postprocessing.

These data should not be used for navigational purposes.