Eat as many fish as possible. Eating many fish in quick succession start a score multiplier in the upper left corner. Continue to eat fish without stopping and the multiplier will grow. Some fish have a gold appearance. Eating those fish will reward you with bonus coins. Eating anything will build the gold rush bar at the bottom. When full, all fish will turn gold for a limited time. When you encounter a school of fish, eat all of them to collect a "School's Out" bonus for more points.