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1 He felt anxious.

2 He thought of jumping overboard and swimming away from the boat with the tiger.

3 He couldn't jump and swim away because, firstly, the land was hundreds of miles away; secondly, he had nothing to drink or eat; thirdly, there were sharks in the water. (Besides, the boy didn't know which way to go and how to keep warm)

4  He thought he was going to die.

5 In the end he decided not to die but to work hard in order to survive.