Here is the full list of all 17 Umihara Kawase Shun Steam Edition achievements.
Catch all enemies
Catch all Squids during Squid battle
Finish all doors
Obtain all backpacks
Visit all stages
Let 3 birds land on body at the same time
Finish Pufferfish battle with only blowing it away twice
Use door that returns to Stage 0
Travel upwards 2 screens or more without touching the floor
Finish Stage 0 within 10 seconds
Finish Stage 0 within 15 seconds
Make a catch after moving more than 2 screens with lure attached to the enemy
Finish "UmiharaKawase Shun" without losing a life
Catch 3 Flying Fish that jumps from the bucket
Catch all Kid Frogs during Tadpole battle
Catch Sharksucker thrown by Shark while in air
Finish "UmiharaKawase Shun"