Survival chief is a Reef Shark's mission. It requires your shark to survive for 4 minutes. If successfully completed, it rewards you with 100 coins.
How to find and complete
Go right and down, it is found in a small cave. To complete it, try to avoid stingrays more than ever, and clean the most of them in gold rush. If you die, and you have a gem, using it might not be a that bad of an idea.