Idiom Definition:
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"to rock the boat"  
    to make a challenge to a stable and comfortable situation
    
       usually by criticizing or trying to change the situation
       
    
Synonyms:
boycott, break, censure, combat, defect, defy, disobey, dissent, fight, insurrect, insurrection, mutiny, oppose, remonstrate, resist, revolt, riot, rise, secede, status quo, upset
 
 
  
     
  
Literally, 
rocking the boat ... 
  
Technically this is a canoe which is a type of boat.