The setting of "The Little Mermaid" varies depending on the version:

• In Hans Christian Andersen's original fairy tale, the story is set in Denmark, reflecting the author's nationality. The underwater kingdom and the prince's palace are imagined to be in or near Denmark, and there is a famous Little Mermaid statue in Copenhagen

• In Disney's 1989 animated film, the underwater kingdom of Atlantica is located under the Atlantic Ocean. However, the prince Eric's castle and the surrounding human town appear Mediterranean or Southern European in style, with white marble-like buildings, tropical flora such as palm trees and flamingos, which do not match Denmark's environment. This suggests the Disney film is set in a Mediterranean-like region, possibly on an island in the Mediterranean Sea

• The 2023 live-action remake of Disney's "The Little Mermaid" appears to be set in the Caribbean, as indicated by the cultural elements Ariel encounters in the town

In summary, the original tale is set in Denmark, Disney's 1989 film is likely set in a Mediterranean-inspired location, and the 2023 remake shifts the setting to the Caribbean. The underwater kingdom of Atlantica remains a fictional underwater realm in all versions.