The Sims 4: 10 Expansion Packs Fans Demand
7. Underwater Life Expansion Pack
The Underwater Life Expansion Pack would be a neighbourhood that's under the sea. Your Sim would either be a mermaid or an Atlantic native.
It could be a combination of Atlantis: The Lost Empire and The Little Mermaid.
If you play as a mermaid you could discover new items that are dropped into the ocean, train dolphins and sharks as your pets and hunt for food with fishing spears and if you play as an Atlantic native, you would have different magical abilities, you'd also have to hunt/fish for food and you'd have to live in huts.
It would be very similar to Sims 3 Island Paradise or Sims Castaway, but you'd be playing in the city of Atlantis or in the deep blue sea.