In the vast Atlantic ocean, a mysterious and vital ecosystem floats and thrives, vital at sea but disastrous on shore—the Sargassum seaweed. Sargassum is a visually captivating 90 min documentary that uncovers the seaweed's ecological significance and the intricate relationships it holds with marine life and humanity. Experts shed light on the critical role Sargassum plays in marine biodiversity, acting as a nursery and a sanctuary in the open ocean. However, the documentary takes a poignant turn as it investigates the alarming proliferation of Sargassum, particularly in the Caribbean and southern US. Once a symbol of ecological balance, Sargassum has now become an environmental menace, overwhelming coastlines and disrupting local economies. Scientists and environmentalists discuss the factors contributing to this crisis, including climate change and nutrient pollution, which have exacerbated the growth of Sargassum. The documentary also explores innovative solutions and ongoing efforts to mitigate the problem, showcasing the resilience and ingenuity of affected communities in the Caribbean, Mexico.