In “The Last of the Sea Women,” an extraordinary band of warrior grandmothers fight a gritty battle against vast ocean threats. Often called real-life mermaids, the underwater haenyeo of South Korea’s Jeju Island are renowned for centuries of diving to the ocean floor, without oxygen, to harvest seafood for their sustenance. Today, with most of the haenyeo now in their 60s, 70s, and 80s, their traditions and way of life are in imminent danger. But these fierce, funny, and hardworking women refuse to give an inch, aided by a younger generation’s fight to revive their ancestral way of life through social media. Examining what drives haenyeo young and old, this moving documentary focuses on their close friendships, savvy independence, and infectious sense of empowerment, unfolding in an uplifting tale of women taking on global powers to protect their beloved ocean and inspire a new generation.