When scoring points, that will go toward filling up the Gold Rush bar. When the bar fills, you'll enter Gold Rush mode, which spawns several extra fish and also fills your health. You will also become invincible while the effect lasts, and you can earn points by running into objects that would otherwise hurt you. The exact duration of that effect depends on the variety of shark you are using, and also any accessories equipped. While in Gold Rush mode, make sure that you move around quickly and eat everything in sight, while avoiding dead ends and long tunnels where you won't have much chance to eat a lot before the effect fades.
After getting your first daily bonus, leave the game and double tap you home button(iPhone). Stop game running in background, then change the date and time settings to one day ahead. Now play again to get the bonus again. Rinse and Repeat.