Bioacoustic data from an Acoustic Zooplankton Fish Profiler (AZFP) deployed in the MOSAiC Central Observatory the four AZFP frequencies (38, 125, 200 and 455kHz) are published. This echosounder was deployed on February 16th, 2020 and retrieved on August the 2nd 2020, after 168 days of operation. The conditions during deployment are described as second year ice in the MOSAiC Central Observatory. The AZFP was connected to the surface buoy with a 5 m long umbilical cable and acoustic beam of the echosounder was pointed downward. Due to its dimensions, weight and color this buoy type was sometimes referred to as the “white monster”, or “AZFP-2”, “POPEDOWN” or “ITO306” in the different MOSAIC-related reports.Data from the Iridium messages used to control the surface buoy are also included. These include geographical position together with date and time stamp of the AZFP. An independent GPS tracker of the type XEOS Rover was attached to the AZFP and its GPS track is also part of this data set.For the AZFP data, the initial and final deployment (.DPL) and configuration (.XML) files are included. these describe the instrument configuration and sampling plan. The bioacoustics data sets (.01A,.01B, ..., .02A,...) are consecutive, divided hourly. the first two digits describe the phase of the sampling program being used when the file was created while the letter B and C are for files generated within a same hour when the process is interrupted, for example, when backing up the data from the echosounder.During MOSAiC two AZFPs were deployed. The other one had an AZFP pointing upwards, see doi:10.1594/PANGAEA.953621.