The objective is to get to Black Beard’s hidden island to find his treasure. During your adventure you will win gold coins every time you brush.
When you brush the zone indicated by the smart guide for the right amount of time, you will win the gold coins you find on your way.
But, once you get to level 9 (Corsaro Island) it gets more difficult: if you are not brushing correctly then the coins on your path become transparent. This means you are in the right zone in your mouth but you are not brushing the right surfaces. If you adjust your brushing so it follows the smart guide then the coins will reappear!
While you brush you can also pick up jewels that will be changed into gold coins.
The jewels are worth the following:
Emerald = 5 gold coins
Sapphire = 25 gold coins
Ruby = 50 gold coins
To get to Bourbade Island you need 3,000 gold coins.
To get to Corsaro Island you will need 24,000 gold coins. Finally, you will need 85,000 gold coins to get the Golden Unicorn galleon and go to Black Beard’s secret island.