After learning reef basics with the Planting 101 task, Squirt invites Nemo to play a game of Hide and Seek. Squirt hides in the reef and it's up to Nemo to find him.
To look for him, tap on a plant. If the plant turns purple, that means you are not far away, but you are not that close either.
Tap other plants nearby; once a plant turns red, that means you are really close! Keep tapping in that area until the hidden sea creature reveals itself.
Find all the hidden fish with your allotted moves before time runs out to win the game. Your rewards are likely to be Common or Rare Spines among other items. Spines are invaluable for opening Mysterious Chests!