There has long existed a need for pelagic tide and current measurements, but the technology for making such observations has been developed only recently. In 1965, an international working group on deep-sea tides was formed (now sponsored by IAPSO, SCOR, and Unesco) that would concern itself with the exchange of information on instrumentation and analysis and with the formulation of a worldwide data acquisition program.
Some pelagic tide observations have now been obtained by pressure sensors on the sea bottom connected by cable to the surface [Eyri`es, 1968] or to shore [Nowroozi et al., 1968] and by self-contained bottom instruments that record internally and are recalled to the surface by an acoustic signal [Snodgrass, 1968] and time-release device [Filloux, 1968, and Hicks et al., 1965]. The equipment described by Snodgrass and by Nowroozi include current meters measuring speed and direction. The over-all objectives of the deep-sea tide program are described by Munk and Zetler  and Cartwright .