Here is the full list of all 30 Nightmares from the Deep 2: The Siren's Call achievements worth 1,000 gamerscore.
Finished all the games of Mahjong.
Finished a game of Mahjong in less than 1 minute.
Completed the game on expert difficulty
Finished half of all the games of Mahjong.
Completed the bonus adventure.
Completed the game.
Got to the contents of Davy Jones' chest.
Finished all the puzzles without skipping
Finished any Hidden-Object Scene with less than 3 mistakes.
Gathered a twelve golden fish tokens.
Got to the top of the lighthouse and saw what's underneath.
Enabled your ally to return to work.
Prepared a spiked coffee.
Found your way inside the lighthouse.
Found all secret sea horses.
Finished 10 Hidden-Object Scenes in a row without using any hints.
Fixed the radio.
Found 4 Hidden Objects within 4 seconds.
Entered the shipwreck cemetery.
Finished a Hidden-Object Scene in less than 1 minute.
Saved your ally from a tight spot.
Found a direct way to get behind the closed gates.
Finished 5 puzzles in a row without skipping.
Visited a local bar.
Finished a puzzle in less than 1 minute.
Witnessed the devastating attack of the sea monster.
Arrived on the pier.
Finish all Hidden-Object Scenes.
Find all morphing parrots.
Find all hidden octopi.