That's why I'd like to share two of my favorite books on the subject. The first is actually a picture book by Steve Jenkins just released this week called DOWN DOWN DOWN: A JOURNEY TO THE BOTTOM OF THE SEA. It's a beautifully illustrated introduction to all of our ocean's inhabitants, starting at the surface with sharks and dolphins and progressively going deeper through the sunlit zone, the twilight zone and the dark zone until reaching the abyssal plain and then spotlighting the Marianas Trench. There is a lot of helpful scientific information presented in an easy-to-understand and fun way. Recommended for ages 4 and up.
The second is a book of extraordinary underwater photography by Claire Nouvian called THE DEEP. In addition to the jaw-dropping pictures of ferocious sea beasts (many of which are tiny in real life), there are essays by top oceanographers and marine biologists. So not only is it a blast to flip through and look at the pictures, you also learn a lot by reading the text. Recommended for ages 10 and up.