The Earth has one big water system with many features.This app has amazing images and footage of Ocean Science. It consists of seven principles of Ocean Science: (1) One Ocean, (2) Supreme Power, (3) Out of the water, (4) The origin, (5) Another world, (6) The great provider and (7) The final frontier. You can explore each of the principles using the document version which allows you to annotate notes along the way. You can also explore them visually. I recommend this iPad app for Y4-Y9.