The stranding of floating seaweed (Sargassum) rafts is a recent regular phenomenon affecting Atlantic coastal nations of the Caribbean, Central America and tropical West Africa. While the reasons for this unusual landfall are not yet fully understood, affected communities must find ways to deal with the seaweed, which can smother beaches, block harbours and become toxic to humans and wildlife as it decomposes, with adverse effects on vital fishing and tourism activities. Its effects are felt most strongly by vulnerable small island developing states.