Below is a figure illustrating an Ocean Bottom Seismograph (OBS).  This particular type of OBS, also contains 2 tiltmeters (an X & Y component), and 4 inclinometers. A paper describing results from a deployment of these instruments to study tilt signals on the seafloor can be found here (Tolstoy et al. 1998). This OBS fleet is run by Prof. John Orcutt at IGPP, Scripps Institution of Oceanography.