Seaweed, contrary to popular belief, is edible. In fact, with the rising popularity of sushi, more people are eating it these days. But this accounts for only one way in which this food is consumed. In fact, according to the BBC, there are more than 10,000 types of seaweed in the world. Since it grows naturally in the ocean, which covers 70 percent of the Earth’s surface, seaweed is truly a sustainable food.