Ocean Master Achievement
Complete underwater special levels
There are three Underwater special levels that unlock after you've completed puzzle #15 of the basic levels. You can access them by selecting the hexagon icon to the right and between puzzles #2 and #3.
Note: There is a fourth level in this group, accessed by selecting the hexagon marked with an infinity symbol. This level is not necessary for any achievement.
Refer to "Hard Mode Totems Master" for more information.