Several things spring to mind:
1. A brand of very high end audiophile speakers made by B&W. Nautilus speakers create exceptional sound by eliminating echoes from the back of the box by using a speaker shape reminiscent of a nautilus shell.
2. The next generation file manager for GNOME (v2.0).
3. The animal that the previous two were named after, a cephalopod of the phylum Mollusca, that as a species, has survived relatively unchanged for millions of years in the oceans, much like the coelacanth.
The amazing thing about this creature is the design of its shell. As the nautilus grows, it creates additional septa in its shell, creating new chambers within it. These chambers are linked by a tube through which the nautilus controls the amount of water and gas there are in each chamber.
With its watertight chambers providing adjustable bouyancy, the nautilus uses a funnel it has for jet propulsion by squirting out water in the direction opposite to whatever direction it wishes to go.
A nautilus can ascend from 2000 ft below sea level to sea level without any problems arising from the difference in pressure.