2.5 stars.
I was 2/3 of the way through this book before I realized that this book is not simply about oceans, it is about ocean currents. Four of its five chapters are about ocean currents, and the fifth chapter is about the environmental damage that humans are doing to the ocean. It was a good book, I just found the topic of currents to be more challenging to read about than I thought, and I wish that the book had been more clear that it was about specifically ocean currents and not the ocean as a general topic. A little knowledge of physics could be helpful because they talked a lot, although not in a mathematical way, about fluid dynamics.