Here is the full list of all 22 Sea of Solitude achievements.
Reached top of the Skyscraper
Finished Level 1
Travelled a long distance by boat
Travelled very far by foot
Made it through school
Fired 30 flares
Opened a path through water
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
Jumped headfirst into the water from a high point
Eaten by Whale 20 times
Swam a very long distance
Swam a long distance while Whale was around
Finished Level 2
Finished Level 3
Finished the game