The HydrOctopus consists of 4 hydrophones connected to the same datalogger, to allow high-precision location of shallow events within the antenna.  The goal of the instrument is to study secondary (entrained) hydrothermal circulation associated with the highly active Tour Eiffel and Montségur vents of Lucky Strike volcano on the Mid-Atlantic Ridge.  Data are provided in miniSEED format, metadata in StationXML format. Network code is 4G.  Station codes are LSVHJ (2016-09 to 2017-07) and LSVHK (2017-07 to 2017-09).  Channel codes are all CDH and location codes are 01-04. The data and metadata can be processed using several seismological software suites, including obspy.  Data are organized in Seiscomp Data Structure (SDS), allowing specific channels or dates to be read using SDS-savvy readers such as obspy’s filesystem.sds client.