What to know as a giant mass of seaweed is coming to shore

The Great Atlantic Sargassum Belt, a 5,000-mile-long belt of seaweed weighing more than 11 million tons, is threatening to wreak havoc in the coastal waters and beaches of the Atlantic Ocean. It's so big that it can be seen from space, spanning the tropical Atlantic from West Africa to the Caribbean. Oceanographer Ajit Subramaniam joins John Yang to discuss.