Fish have a specialized sense organ called the lateral line which works much like radar and helps them navigate in dark or murky water.  

Some fish, like sharks, don’t posses an air bladder to help keep them afloat and must either swim continually or rest on the bottom.

March 29, 2013 | Categories: From the Gremlin

 

Some fish, like sharks, don’t posses an air bladder to help keep them afloat and must either swim continually or rest on the bottom.