Here is the full list of all 51 Immersion achievements.
Complete level 7
Complete level 6
Complete level 6 with 3 stars
Kill 3 peaceful fishes in a single game
Kill a random fish
Complete level 5 with 3 stars
Complete level 5
Complete level 4
Complete level 4 with 3 stars
Complete level 3 with 3 stars
Complete level 3
Get caught by a shark
Complete level 2
Complete level 2 with 3 stars
Kill a shark
Complete level 1
Complete level 1 with 3 stars
Complete level without shooting
Run out of oxygen
Take a shot
Miss a shot
Get your first chest with treasure
Complete level 8
Complete level 9
Complete level 10
Complete level 11
Complete level 12
Complete level 13
Complete level 14
Complete level 15
Complete level 16
Complete level 17
Complete level 18
Complete level 19
Complete level 20
Complete level 7 with 3 stars
Complete level 8 with 3 stars
Complete level 9 with 3 stars
Complete level 10 with 3 stars
Complete level 11 with 3 stars
Complete level 12 with 3 stars
Complete level 13 with 3 stars
Complete level 14 with 3 stars
Complete level 15 with 3 stars
Complete level 16 with 3 stars
Complete level 17 with 3 stars
Complete level 18 with 3 stars
Complete level 19 with 3 stars
Complete level 20 with 3 stars
Complete all levels
Complete all levels with 3 stars