next question: People often describe what as a giant wall of water?
Options:
- backpack
- allen key
- snowball
- ocean
- tsunami
reasoning:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Tsunami is a giant wall of water. People often describe tsunami as a giant wall of water. The answer is tsunami.