Recent technological advances in manned and unmanned undersea vehicles have overcome some of the limitations of divers and diving concentration became limited because of undersea pressure which affected their speech organs, communication among divers was difficult or impossible but today, most oceanographers make observation by means of instruments of the ocean floor are made not only by divers but also by deep-diving submarines some of the these submarine can dive to depths of more than seven miles and cruise at depths of fifteen thousand feet radio equipped buoys can be operated by remote control in order to transmit information back to land-based laboratories, including data about water temperature, currents, and weather