The intended audience for this book is age 8-14, but the really cool thing about it is that it actually makes a really good overview for any age. The book was published 40 years ago so much of the information and photos is totally dated. But that is not too much of a hindrence. Given that the book is old, there is still a lot of information that is still relevant. For instance, the book explains the early history of deep sea exploration and narrates how early wreck divers and commercial divers took their life in their hands when they went below. The black and white photos seem charming and the author is respectful without being worshipful for people who work or play in the ocean.