Here is the full list of all 21 Wooden Sen'SeY achievements.
Finish the underwater level without dying
Defeat the final boss with bombs only
Collect all the SeY bottles in each level
Slice all the enemies in each level
Collect more than 4 000 SeY bottles
Slice more than 999 enemies
Earn your first gold medal
Collect enough SeY to save the village
Finish the boss's whining head
Destroy the boss' ship from underneath
Escape the cage
Die more than 15 times in one level
Collect all the SeY bottles in one level
Beat our time in one level
Slice all the enemies in one level
Smash the ground with your axes for the first time
Beat our time in each level
Destroy the boss' ship without touching the ground
Collect all bronze medals
Collect all silver medals
Collect all gold medals