Magic Water Murder

A famous magician, Jovan, is performing in front of a live audience. He has to stay in a trunk inserted in water for a full 3 hours. He is put into the water when a spectator, Amit, challenges that the magician is cheating. Amit jumps into the water and opens the trunk - it is empty. But where is Jovan? CID is on the case and upon investigation, they find Amit's dead body and then find Jovan's dead body. Who killed these two men and what is the secret of the trunk?