Disney's live-action The Little Mermaid is coming to theaters, and with the new trailer and poster now revealed, Blu took one look and thought something seemed a bit off! Sure enough, my good friend Wox — fish expert and author of Ocean Naturalist — had already created an annotated breakdown of the creatures surrounding The Little Mermaid's world. The story is set in the Atlantic, yet almost every animal pictured is a non-native species. Come along with Blu and see who wandered onto the wrong set!
Poster source: Disney. Yellow annotations source: Li Cheng-Lu
Sebastian, the Little Mermaid's Sidekick, Is Actually a Land Crab
Sebastian, the melodious companion at the Little Mermaid's side — have you ever wondered, "Is he a lobster or a crab?" Wox has the answer: he's actually a red land crab. Based on the character model in the film, he appears to belong to either the family Ocypodidae (ghost crabs) or Gecarcinidae (land crabs), with a tall body and slender legs. These land-dwelling crabs are very different from their aquatic relatives — they have adapted to breathing air, and if you submerged them in the ocean, they would likely drown!
The World's Most Famous Red Land Crab — The Christmas Island Red Crab
The most well-known red land crab in the world is the Christmas Island red crab (Gecarcoidea natalis), found primarily on Christmas Island in the Indian Ocean. Unlike most crabs, they live in the forest, moving through the greenery as scavengers that clear away dead leaves and branches. They still require a highly humid environment, so during the dry season they burrow into the moistest soil and only emerge when it rains. When the wet season arrives — around November each year — they emerge en masse for the famous Christmas Island red crab migration, making a beeline for the beach to spawn.
Taiwan's Red Land Crab — The Intermediate Sesarmid Crab
Blu also has another fun fact to share: Taiwan has its own red land crabs, most commonly the intermediate sesarmid crab (Orisarma intermedium). They tend to appear in estuarine vegetation zones along tropical coasts, relying on the moist riverbanks to survive. Only during the rainy season do egg-carrying females migrate to the sea.
Intermediate sesarmid crab. Photo Credit: Li Cheng-Lu
A Freshwater Fish from the Amazon — The Arapaima
"Little Mermaid~ The salt is killing me!"
Arapaima. Photo Credit: Li Cheng-Lu
On the right side of The Little Mermaid poster, two freshwater fish from the Amazon River make an appearance. The larger one is the arapaima (Arapaima gigas), also known as the pirarucu or elephant fish. It inhabits the Amazon River basin in South America and first appeared roughly 100 million years ago, earning it the nickname "living fossil." In real life, it reaches body lengths of about 3 to 6 m and can weigh up to 200 kg, making it one of the largest freshwater fish in the world.
Its enormous, distinctive scales act like heavy armor, allowing it to glide safely even through piranha-infested waters. In The Little Mermaid's underwater world, however, the saltwater would disrupt its osmotic balance, causing the water levels inside its body to collapse — it simply couldn't survive.
How Does the Eartheater Fish Eat Dirt?
The small fish below the arapaima in the poster is the eartheater (Geophagus sp.), a cichlid also from the Amazon River. The name comes from its habit of scooping up sand and sediment from the riverbed, filtering out the tiny insects and shrimp inside — it looks exactly like it's eating dirt! Just like the arapaima, the salty seawater in The Little Mermaid's world would likely be a death sentence.
Indo-Pacific Residents That Also Wandered Into The Little Mermaid's World
The vast majority of fish in the poster are not native to the Atlantic at all — they're species from the Indo-Pacific region. This region, often abbreviated as the Indo-Pacific, is known for its warm climate and clear waters. Beautiful coral reefs frequently form along its coastlines, and the famous Coral Triangle — home to the world's highest marine biodiversity — falls within this area. Let Blu introduce you to these non-native species that have crashed The Little Mermaid's world!
Scalefin Anthias
The scalefin anthias has the scientific name Pseudanthias squamipinnis. It can also be found in Taiwan's eastern, northern, and southern waters, as well as around Orchid Island and Green Island, though it prefers warmer water so numbers are lower in the north. These sociable fish are commonly seen schooling above reef areas to feed on plankton, and typically only one larger male is present in each group. Notably, before mating the male's coloration turns white with excitement, and males of different groups often chase and compete with one another for mating rights with females.
Scalefin anthias (Pseudanthias squamipinnis). Photo Credit: Lin Yu-Ping
Undulate Triggerfish
The triggerfish in the lower-left corner of the poster is the undulate triggerfish (Balistapus undulatus). It has no grooved depression in front of the eye, and its body is marked with vivid orange-yellow diagonal stripes, making it easy to identify. This carnivorous triggerfish feeds on a variety of benthic organisms and will occasionally actively hunt small fish.
Undulate triggerfish. Photo Credit: Li Cheng-Lu
Lionfish
The Lionfish in the lower-right corner of the poster bears a strong resemblance to the spotfin lionfish (Pterois antennata), with its slender, elongated pectoral fin rays and vivid coloration. But its personality is quite the opposite of its showy appearance — naturally shy, it usually rests alone in hidden crevices among the reef, keeping its venomous dorsal spines facing outward as a deterrent. With a small home range, it rarely strays far from its resident reef or coral.
Spotfin lionfish (Pterois antennata). Photo Credit: Li Cheng-Lu
Pennant Bannerfish
The bannerfish on the poster appears to be the schooling bannerfish (Heniochus diphreutes), which looks very similar to the moorish idol and is often mistaken for it. Look closely, though: the schooling bannerfish has a shorter snout, and its third black bar ends at the tip of the anal fin. Unlike the moorish idol, it is far more commonly seen schooling in open water to feed on plankton — sometimes in massive groups of hundreds or even thousands of individuals.
Schooling bannerfish (Heniochus diphreutes). Photo Credit: Li Cheng-Lu
Yellow Tang
The yellow tang has the scientific name Zebrasoma flavescens — a small, bright yellow surgeonfish that inhabits tropical environments with abundant coral growth, especially rocky reef areas rich in stony corals. It feeds on algae, using its elongated snout to forage in narrow crevices. Its striking appearance has made it very popular in the aquarium trade, but overharvesting has already significantly reduced wild populations!
Yellow tang. Photo Credit: Li Cheng-Lu
Coral Grouper
The coral grouper (Cephalopholis miniata) visible in the lower-right corner of the poster is a small Grouper that typically hides in coral reef crevices, its body covered in vivid blue spots. Wox also dropped a teaser: a more detailed profile of the coral grouper will appear in Ocean Naturalist 3, so don't miss it!
The Humphead Wrasse Has Arrived!
The Humphead Wrasse — another species found across the Indo-Pacific — has a connection to The Little Mermaid too. Perhaps because it's such a star species of the sea, it earned a spot in the poster. Let's get to know it!
Humphead Wrasse. Photo Credit: Lin Yu-Ping
Humphead Wrasse
The Humphead Wrasse, also known as the Napoleon Wrasse, has the scientific name Cheilinus undulatus. Its signature features are a steeply rising hump on the forehead and thick lips. It is also remarkably long-lived, easily surpassing 30 years of age. Interestingly, all Humphead Wrasse are born female and take 5–7 years to mature; between the ages of 8 and 9, some females undergo a sex change and become male.
The Humphead Wrasse is commonly distributed across tropical coral reef waters from the Indian Ocean to the Pacific. In Taiwan, sightings have been recorded around Green Island and Kenting, among other locations. With a maximum body length exceeding 2 m and a weight of around 200 kg, the Humphead Wrasse commands considerable economic value — but consider this: rather than fishing for them, allowing them to become underwater celebrities that draw divers and tourists could generate far greater economic returns.
What's more, the IUCN listed the Humphead Wrasse as Endangered as far back as 2004. As a high-level predator in the food chain, it is also an indicator species for coral reef ecosystems — protecting the Humphead Wrasse means protecting the entire reef ecosystem.
Humphead Wrasse. Photo Credit: Jian Chen-Yu
Who Else Wandered Onto the Wrong Set in The Little Mermaid Poster?
Beyond the species introduced above, quite a few more fish in The Little Mermaid poster are out of place — including a northern gannet from the temperate North Sea, a Red Sea raccoon butterflyfish (diagonal butterflyfish) from the Red Sea, an emperor angelfish from the Indian Ocean, and a sleek unicornfish from the Indian Ocean. Is there a particular species you'd like to learn more about? Head over to BlueTrend's Facebook page and leave a comment to let me know!
The live-action The Little Mermaid is scheduled to open in Taiwan on May 25. If you're planning to see it, don't forget to look out for these highlights — and feel free to come share with Blu any other marine life you spot.
Many of the marine creatures introduced above can be found in volumes one and two of Ocean Naturalist, with richer and more complete descriptions inside. Some species are set to appear in volume three, so stay tuned. Blu highly recommends picking up Ocean Naturalist and leveling up your ocean knowledge!
A word from fish expert Wox: After sharing this post, it sparked a lively response online. I even saw some friends reply: "What's so strange about it — all the oceans are connected." But think about it this way: if a koala appeared on the savanna in The Lion King, how would that feel? Because people are more familiar with land animals, seeing a lion and a koala together would seem bizarre. But because most people aren't familiar with marine animals, seeing them all mixed together doesn't register as odd. This is exactly why we believe ocean education is so important. The oceans of the world each have their own unique ecological character — and this "mixed-bag" poster is a perfect invitation to get to know them better!
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