Sunless Sea: Zubmariner Edition

Step 1: Get a lover by carousing in Fallen London each time you visit until the event for a lover pops. You can only do this once per visit. When the event pops asking you whether or not you want to keep the locket, pick yes and keep it.
This will unlock:

Step 2: Continue to visit your lover, by carousing. After 2-3 visits you will receive a letter informing you they conceived/adopted a child.
Step 3: Return to Fallen London and take the "Time with your Family" action in your lodgings. You can only do this action once per visit to London. Each time you spend time with your child you will be able to increase their sea fever with the following items:

"Memory of Distant Shores" = 5 Fever
"Zee-ztory" = 5 Fever
"Vision of the Surface" = 5 Fever
"Live Specimen" = 7 fever
"Outlandish Artefact" = 7 fever
"Judgements' Egg" = 15 fever

Step 4: Keep bringing items until your kid reaches 25 sea fever. Immediately you will receive an event to take him on your ship or leave him home. Take him on your ship to unlock the achievement.