'I Wonder Why the Sea is Salty' and other questions about the Oceans, from Kingfisher books. Rrp £5.99 so get it for LESS than half price here! Colourful, surprising and full of information, the I Wonder Why books have set thousands of young minds buzzing. I Wonder Why the Sea is Salty is the perfect introduction to the Oceans, featuring mountains under the sea, singing whales, deep-sea divers and more. Glossy paperback. Approx 28cm x 23cm.