context: A swimming instructor, Cheon-soo, loses everything to gambling. He's stuck with no means of income and a huge debt to pay off. The man who loaned him the money, Kang comes to him with a proposition. He invites Cheon-soo to become a marine boy, those who swim across the ocean to smuggle drugs. Cheon-soo decides to take the chance and puts his life at stake for the last time. Together Kang and Cheon-soo come up with a meticulous plan. Yoo-ri is the daughter of Kangs best friend. Since her father died, Kang has been looking after her in his friends place. Yoo-ri believes that Kang is responsible for her fathers death and secretly waits for her chance to get her revenge on him. Oblivious of this, Kang grows affection towards her which leaves him feeling guilty. Yoo-ri and Cheon-soo develops feelings towards each other and plot to go behind Kangs back and take the drug money for themselves.Former national swimmer Cheon-soo dreams of travelling to Palau, and to fund his trip he works as a swimming instructor by day while gambling at night. However, after losing a game of poker he finds himself heavily in debt and in trouble with the loan sharks. Kang, the head of a local drugs syndicate, offers to pay off Cheon-soo's debts; in return, Cheon-soo must work as a "marine boy", a mule who smuggles drugs across the open waters.
  Knowing the danger he faces, Cheon-soo tries to make a run for it, but he is arrested at the airport by police detective Kim Gae-ko. Kim is intent on capturing Kang, and faced with no other choice, Cheon-soo agrees to work as a spy on his behalf. His situation becomes further complicated when he falls for Yu-ri, a jazz singer under Kang's charge and the daughter of Kang's best friend. But Yu-ri suspects Kang of killing her father, and she and Cheon-soo plot to take the drug money for themselves. [D-Man2010]
question: What kind of singer is Yu-ri?
answer: Jazz singer