In recent years, large amounts of Sargassum have been washing up on beaches from the Caribbean to west Africa. This floating seaweed drifts on the oceans currents. New research explores how the Sargassum might grow while it is meandering along the currents, not just where it floats, combining both ocean physics and seaweed biology for the first time to understand the distribution patterns. Knowing could eventually help predict its arrival and impact on beaches around the world.