Here is the full list of all 22 Sea of Solitude achievements.
Travelled a long distance by boat
Made it through school
Travelled very far by foot
Fired 30 flares
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 the first flare
Collected all bottles
Shooed all Seagulls
Respawned on couch in Skyscraper
Got grabbed by waterhands 10 times
Eaten by Whale 20 times
Swam a very long distance
Swam a long distance while Whale was around
Finished Level 1
Reached top of the Skyscraper
Finished Level 2
Finished Level 3
Finished the game