Here is the full list of all 16 Drowning achievements.
Finish the third secret ending
Find and complete all the game endings
Finish the game's main ending
Find the secret sock
Finish the second secret ending
Try to climb the hill in the dark forest
Find the secret ball on the Christmas tree
Find the secret candy
Try to climb the large rock at the beginning of year 12
Try to fall off the bridge 10 times in year 11
Finish the first secret ending
Find the secret candle
Find the secret snowman
Find the secret gift box
Try and swim in the pond in year 8
Start a new game for the first time