Nina investigates why the sea is so salty with the help of Bud, her taste neuron. Experimenters Lydia, Olivia and Ruan visit Nina in her lab and use their senses to work out what salty means! Nina explains that our bodies need some salt but that too much salt is bad for us. Then they look at some salt under a microscope and discover that the salt we use in our food can be found on the land and in the sea. They all go to a stream and have a rubber duck race! There they discover that rivers and streams can carry things to the sea. Finally, back in the lab, they do an experiment to show how the rain washed salt from the land into the sea over millions of years, making it saltier and saltier!