Depth

• It is considered an ecological zone and is defined as everything beyond a depth of 3,300 fathoms—or 3.75 miles. Life is seldom studied at this depth because of the technical difficulties involved.
  
  

Methods of Study

• The two methods used to find and study deep-sea life are camera observation and trawl-based capture. Trawls are not completely reliable because it is difficult to know at what level the sea-life enters the net.
  
  

Snailfish

• Snailfish are soft, tadpole-shaped, scaleless fish that grow to about a foot in length. Camera observation has revealed these fish at a depth of 4.78 miles.
  
  

Sea Cucumber

• Sea cucumbers belong to the same family as starfish and sea urchins. They are odd-looking creatures with up to 30 tentacle-like tube feet surrounding their mouth.
  
  

Food Chain

• Snailfish feed on crustaceans and cucumber fish feed on the droppings and carrion of other sea creatures as well as microscopic organisms. Shrimp are the primary crustacean living in the hadal zone, and they feed on microorganisms.
  
  

Plants

• There are no plants in the hadal zone because sunlight does not penetrate deep enough to allow photosynthesis. The maximum depth at which photosynthesis may occur is 656 feet.