Most of these mermaids are just "normal" creatures from the bottom of the sea that have evolved to look vaguely human, as they used to attract and hunt humans as in the ancient legends about mermaids.
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Not available to stream in India right now.
Monster High: Scaris City of Frights
The Witcher: Nightmare of the Wolf
Abraham Lincoln Vampire Hunter: The Great Calamity
Welcome to Smelliville
The Witcher: Sirens of the Deep
Cranston Academy: Monster Zone
A Tooth Fairy Tale
The Spine of Night
The Fantastic Flying Books of Mr. Morris Lessmore
Monster High: Haunted
DC Showcase: The Phantom Stranger
Basilisk: The Serpent King
Van Helsing: The London Assignment
Monster High: Why Do Ghouls Fall in Love?
Nightbreed
How to Train Your Dragon: Homecoming