Here is the full list of all 22 Sea of Solitude achievements.
Swam a very long distance
Shooed all Seagulls
Collected all bottles
Jumped headfirst into the water from a high point
Swam a long distance while Whale was around
Eaten by Whale 20 times
Got grabbed by waterhands 10 times
Respawned on couch in Skyscraper
Finished the game
Finished Level 3
Finished Level 2
Reached top of the Skyscraper
Finished Level 1
Travelled a long distance by boat
Travelled very far by foot
Made it through school
Opened a path through water
Fired 30 flares
Shooed your first Seagull
Collected your first Message in a bottle
Connect with mirror Kay for the first time
Fired the first flare