The Sea Dragon sails through the center of the South Atlantic Ocean carrying researchers from the 5 Gyres Institute on what the film presents as the first scientific expedition to study plastic waste in that stretch of ocean. The crew hauls trawl nets through open water far from any coastline, sorting through the fragments and microplastics they pull up, and the footage stays close to the daily work of sampling and cataloging rather than dramatizing the voyage. Life aboard a small research vessel on a long ocean crossing gets its own attention, from cramped quarters to the routines that structure weeks at sea. The larger aim is to connect what turns up in these nets to the global scale of plastic pollution, treating this one gyre as a single data point in a much bigger problem. The film stays close to the crew's perspective throughout, an on-the-water account of how this kind of research actually gets done rather than a broad survey of ocean plastic.