The Close Encounters with Sirens overviews the themes of pure versus applied sea monstrosities, setting the stage for a deep dive into mythical aquatic beings. It then explores American close encounters with sirens, weaving in cultural folklore and interpretations, before transitioning to anecdotal encounters with unidentified aquatic humanoids, analyzing patterns in personal accounts. This leads into strange interactions between divers and mermaids, considering psychological and environmental factors, followed by legends of mermaids lurking in the ocean's dark depths, emphasizing the mysteries of the deep sea. The narrative shifts to peculiar depictions like mermaids perched on branches, symbolizing their ties to nature and femininity, and expands to broader underwater humanoids compared to traditional mermaid lore. A scientific pivot examines NOAA's declaration that sirens do not exist, contrasting with explorations of various water spirits such as nymphs, maidens, mermaids, and oceanids across cultures and their mythological evolution. Investigations into the historical origins of sirens and their modern transformations follow, including tales of three famous sailors who claimed sightings and their impact on maritime lore. The book questions the existence of legendary unidentified aquatic humanoids, then delves into darker, less beautiful portrayals of mermaids, highlighting their dual nature of allure and peril. It recounts the discovery of a supposed mermaid corpse and societal reactions, leading to discussions on criticisms faced by folklore researchers and the beliefs of communities revering water people. Hoaxes related to these creatures are scrutinized for their influence on public perception, before connecting sirens to UFO phenomena and debating whether mermaids are mere sailor inventions shaped by psychology and environment. The story turns to Ningen as sirens of Antarctic waters, mythological links to deities like Shiva's ultimate weapon, and the Sea Devil's blend of myth and reality. Theories of Hollow Earth tie into hidden sea legends, intersecting with mermaids and the Atlantis myth in popular culture. Environmental concerns emerge with millions of tons of ocean plastic, portraying a defeat of reason and its effects on marine mythology, followed by the dangerous waters of the Baltic Sea and its historical encounters. Specific legends like Kasia, the mermaid from the seal patrol, add cultural depth, leading to mysteries in the Bermuda Triangle and culminating in the folklore of Daeghtine and its modern representations.