nautilus

noun3

1. •
   A marine mollusc, of the family Nautilidae native to the Pacific Ocean and Indian Ocean, which has tentacles and a spiral shell with a series of air-filled chambers, of which Nautilus is the type genus.

   • He was still prepared to go on collecting all that life could offer, like a chambered nautilus patiently adding new cells to its slowly expanding spiral. — 1956
2. •
   A paper nautilus (actually an octopus).
3. •
   A kind of diving bell that sinks or rises by means of compressed air.