ABZU

Unlock White Diving Suit:
When you have found ALL 19 sea shells you will be able to find a door that's located at a few parts in the game where you will be able to unlock and equip a new white diving suit to wear while exploring under water. This new white diving suit will enable you to boost further.

Unlock Chapter Select:
Complete the game once to unlock the Chapter Select option at the 'Main' Menu.