In deep water means in serious difficulty. This answer is correct because the expression has a fixed figurative meaning in English. In an SSC idiom question, students should match the whole phrase with its accepted meaning rather than translate each word separately.

• Classroom example: In deep water can refer to a situation involving in serious difficulty.
• Story example: A writer may use In deep water when describing a situation involving in serious difficulty.
• Exam example: When a sentence contains In deep water, choose the meaning “in serious difficulty.”