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