Full list of all 10 Song of the Deep achievements worth 1,000 gamerscore. It takes around 8-10 hours to unlock all of the achievements on Xbox One.
Commune with the giant seahorse
Defeat the Fomori Boss
Activate the Deeplight
Defeat the Watcher
Meet the Merrow
Destroy the Forbidden City forever
Feed the Queen Leviathan
Purchase all upgrades
Kill a Tremorclaw Crab as Merryn
Pay your respects to the Watcher and drop a flower on her final resting place.