Multibeam data were collected during R/V Sonne cruise 258/2. Data recording was executed during the whole cruise. Eight parallel profiles were measured in north south direction starting on Sri Lanka Shelf at ca. 6°00'N until 3°30'S. Western most profile is following longitude of 80°50'40"E. Neighbouring profiles are continuing to the east with distance of 17.2 km (9.2nm) one to the next. Western most two profiles reach 11°17'S and have length of 1880 km (1015 nm). Profiles 3 to 8 have length of at least 1030 km (556 nm). Across second OBS profile from 03°35'N/082°26'E to 01°29'N/084°01'E a bathymetry profile with length of ca. 400 km (216 nm) and a parallel profile with length of 340 km (184 nm) were sampled. Neglecting repeatedly sailed tracks during OBS operation as well as transits a complete bathymetric profile length of 5777 nautical miles (10.700 kilometers) was sampled. The covered area amounts to 180.000 square kilometers. Data are unprocessed and may contain outliers and blunders. Therefore the data should not directly be used for grid calculations and charting projects but need to be edited furthermore. One file contains a measurement period not exceeding one hour. The dataset consists of 1495 files in Kongsberg Multibeam Processing format (747 files .all, 746 files .wcd). which are compressed with GZIP to size of 14.9GB/50.7GB.