1) On the interactive main menu screen, find a big white circle above "Bamboo Heart" and "Bamboo Ball" bubbles, note the small white circle below it;
2) Find any of the small red fishes;
3) Hold X button to grab a small red fish. Take it to the small white circle, then release X button.
4) Bring 6 small red fishes to the small white circle;
5) The big red fish will appear on the map;
6) Find any of green floating bamboos (one floating bamboo consists of 3 parts);
7) Hold X button to grab a floating bamboo, take it to the big red fish;
8) Feed the big red fish with 2 and 2/3 floating bamboos (8 parts of bamboo in total);
9) Swim to the small white circle and enter it;
10) Hold X to devour everything. After achievement is unlocked, exit the game and enter it again to continue playing.

Repeat the scheme with small frogs instead of small red fishes and big frog instead of big red fish to get "The Green Faced Moon" achievement.