The Chambered Nautilus

The Chambered Nautilus is practically a living fossil.  Many species of nautilus are extinct, with only a few surviving today.  This creature has lived unchanged for millions of years.  The nautilus is a mollusk and part of the Cephalopod family along with the octopi, cuttlefish, and squid.  Similar to it's relatives the nautilus swims by jet propulsion and can reach a speed of up to 2 knots.  It also uses siphons to propel water to escape danger. 
     The nautilus spends most of it's time in deep water (usually about 500-600m), but will move to shallower water during the night to feed among coral reefs.  Since it is found in deep water most of the time it's eyes, unlike it's brethren, are under developed.  They lack lenses, so they see the equivalent of what we see through a pin-hole camera.  Because it's eyes are poor, it relies on smell and chemical sensors in it's tentacles to search out it's prey.