When exploring the question of whether there are really mermaids in the world, we need to clarify how the concept of "mermaids" is usually defined and understood. The mermaid, as a cultural symbol, is widely present in myths, legends, and literary works around the world. In these stories, mermaids are often depicted as mysterious creatures with upper human features and lower fish features.
However, from a scientific perspective, there is currently no conclusive evidence to suggest that mermaids exist in reality. There are fundamental biological differences between humans and fish, which make it impossible for them to form a creature with a human upper body and a fish lower body through natural evolution. Although there are numerous magical creatures in the marine ecosystem, no species that matches the description of mermaids have been found so far.
Of course, it cannot be completely ruled out that science may discover new and unknown species of organisms in the future. However, within the current scientific understanding, mermaids are seen more as a cultural symbol and mythological legend rather than a real-life creature.
From a scientific perspective, there is no real mermaid in the world. This concept is more derived from human cultural imagination and artistic creation. The answer to the question of whether there are really mermaids in the world is: under current scientific knowledge, there is no real mermaid.