To become a mermaid in The Sims 3, your Sim needs the Island Paradise expansion pack and has to eat Mermadic Kelp, which comes either from befriending a mermaid while diving or from the Lifetime Rewards store. Unlike most Sims 3 life states, mermaids cannot be made in Create-a-Sim, so an existing human Sim always has to transform. This guide covers both ways to get the kelp, the one shortcut for starting a mermaid household, what changes once your Sim has a tail, and the salt water rule that can quietly turn them back.
What You Need First
Mermaids arrived with Island Paradise (2013), whose EA store description promises that divers “might uncover sunken treasure or befriend a mermaid.” No other pack adds them, and the pack’s world, Isla Paradiso, is where wild mermaids live.
Two restrictions catch people out, both documented by the community wiki:
- Only regular human Sims can transform. A vampire, werewolf, fairy or other occult who eats the kelp does not become a mermaid. Cure them back to human first; our Sims 3 vampire cure guide covers the most common case.
- There is no mermaid option in Create-a-Sim, even with Supernatural installed. Plenty of guides online claim otherwise; they are describing The Sims 4. The community wiki reports EA kept mermaids out of CAS and off the Exchange on purpose, to make them something Sims earn.
Method 1: Befriend a Mermaid While Diving
This is the free route, and it runs through the Scuba Diving skill.
- Build Scuba Diving until your Sim can reach the Isla Paradiso dive spots (level 2 opens the first). Our Sims 3 scuba diving guide covers the skill and each spot’s level.
- Dive and look for mermaid townies. They appear at dive spots underwater, and a conch shell lets a Sim summon a mermaid they have already met.
- Socialize until the two are good friends. Friendly chat underwater works like any other friendship.
- While both Sims are still underwater, ask the mermaid for kelp. Per the community wiki the interaction is Ask About Fish Parts, and a good-friend mermaid hands over Mermadic Kelp.
- Have your Sim eat the kelp from their inventory.
A bonus from the same friendship: a befriended mermaid can reveal the location of one of Isla Paradiso’s hidden islands.
Method 2: Buy Mermadic Kelp as a Lifetime Reward
If your Sim has lifetime happiness to spend, open the Lifetime Rewards panel and buy Mermadic Kelp. The community wiki lists it at 25,000 lifetime happiness points. It lands in the inventory; eat it and the transformation starts. For a long-running mermaid, the separate Permanent Mermaid reward (see below) is the other one worth saving for.
Shortcut: Starting a Mermaid Household
Because CAS has no mermaid option, the community workaround is to finish creating a household of regular Sims, then give each of them Mermadic Kelp in play. Mermaids are also genetic: the community wiki gives each mermaid parent a 50 percent chance of passing it on, and two mermaid parents always have mermaid children. Children have scaly legs but only grow a tail in water once they reach teen age. If you want twins in that family, our Sims 3 twins guide covers the odds.
Life as a Mermaid
What changes after the kelp, per the community wiki:
- Hydration replaces Hygiene. Swimming in the ocean or a pool, showers, baths and hot tubs refill it; sinks do not. Hydration drains three to four times faster near a fireplace or in the sun. Let it hit zero and the mermaid faints; if nobody splashes water on them, they can die. Mermaids are notoriously bad at fixing this on their own, so a backyard pool is the easiest insurance.
- Food is fish and kelp. Regular meals give little, while raw fish and kelp fill Hunger properly. Our Sims 3 fishing guide keeps a mermaid fed. Vegetarian mermaids get nauseous from fish.
- Water powers. Mermaids breathe underwater indefinitely, never depressurize, swim much faster than other Sims, max out Scuba Diving automatically once they are teens, and are never attacked by sharks.
- The tail. It appears only in water; on land the legs stay scaly. Use a mirror’s Change Scale Color interaction to recolor it.
How Mermaids Turn Back (and How to Stop It)
This is the part most guides skip. A mermaid who goes too long without swimming in the ocean (the community wiki says 48 hours), even while fully hydrated, gets a Salt Water Deficiency moodlet. Leave it and it becomes Adapting to Land, and when that expires, the mermaid becomes a normal human again. A large lake counts in worlds that have one. Buying the Permanent Mermaid lifetime reward removes the rule. More life states and Sims walkthroughs are on our Sims guides hub.
Frequently Asked Questions
Can you make a mermaid in Create-a-Sim in The Sims 3? No. Mermaids cannot be created in CAS in The Sims 3, even with other supernatural packs installed. A human Sim has to eat Mermadic Kelp in play.
Which pack adds mermaids to The Sims 3? Island Paradise. Mermaids, Mermadic Kelp and the dive spots where wild mermaids appear all come with that expansion.
Where do you get Mermadic Kelp? From a good-friend mermaid while you are both underwater, or by buying it with lifetime happiness points in the Lifetime Rewards panel.
Why did my mermaid turn back into a human? Mermaids must swim in the ocean regularly. Skipping it triggers Salt Water Deficiency, then Adapting to Land, and then the life state is lost unless your Sim owns the Permanent Mermaid reward.
Can a vampire or werewolf become a mermaid? Not without mods. Only regular human Sims transform when they eat Mermadic Kelp.