And all flesh died that moved on the earth, birds, livestock, beasts, all swarming creatures that swarm on the earth, and all mankind. Everything on the dry land in whose nostrils was the breath of life died. -Gen 7:21-22
The great flood from Noah's story killed much of the living creatures. But there is one class of animals that weren't touched at all; sea creatures.
For fishes, sharks, whales, etc... it was business as usual. They lived in water and so no amount of rain would affect them negatively.
The situation reminds me of how precise God is with his work. I am sure he could have used some asteroid to hit one of the land masses and cut off all energy source to the earth but that wasn't what he wanted. God does not subscribe to the idea that collateral damage is okay.
For us, it is comforting. Whatever we pass through in life, we can never be accidentally hurt. All that we pass through, all that happens to us, there is a purpose. Granted, as human beings, there are many things we might never really understand God's purpose for, but it is there.
We have only faith to help us hold on to it.