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