  The NEMO prototype detector, called "NEMO Phase-1", has been successfully
operated at 2000 m depth from December 2006 to May 2007. The apparatus
comprises a \emph{Junction Box} and a \emph{Mini-Tower} hosting 16 optical
sensors. Preliminary results are presented. Positions of the optical sensors in
the Mini-Tower were reconstructed through the acoustic positioning system with
high level accuracy. Environmental parameters were analyzed. From data
corresponding to a livetime of 11.3 hours, atmospheric muon tracks have been
reconstructed and their angular distributions were measured and compared with
Monte Carlo simulations.
