The Zubmariner Add-on for Sunless Sea has 24 achievements.
Discover Hideaway
Discover Undercrow
Discover Nook
Discover Scrimshander
Discover The Gant Pole
Use an oasis to increase your oxygen levels
Come face to face with the Constant Companion
Discover Anthe
Discover Rosegate
Discover Aigul
Discover Dahut
Accept a power of the deep zee
Escape underwater combat by resurfacing
Discover Wrack
Discover Low Barnet
Use underwater currents to bear you on your way
Venture beneath the waves
Die of suffocation
Be killed by an underwater creature
Be killed by the Constant Companion
Avoid being killed by the Unexploded Unclear Bomb
Perform an abyssal ritual to encounter Lady Black
Complete the Zubmariner ambition
Collect all of Drownie Love-song, Drownie Counterpoint and Drownie Hymn