Alvin has performed thousands of dives, including one that explored the wreck of the RMS Titanic, and its work in marine biology and oceanography has been featured in many scientific papers.[44] DSV Turtle (DSV-3) of the Alvin class DSV Sea Cliff (DSV-4) of the Alvin class Nemo (DSV-5): an acronym for Naval Experimental Manned Observatory, a test vehicle operated by the Navy from 1970 to 1986. Nemo was a spherical submersible with a transparent acrylic hull, and its primary purpose was to evaluate the utility of the panoramic vision enabled by its design.