I had also learned something far more important: that scientists find out by doing, not by being told. Existing ideas and facts are merely signposts to the future and sometimes misleading ones at that. To linger too long on what is already known, however interesting it may be, is to be distracted from the business of science, which is not just the accumulation of facts, but the pursuit of the new and, if you are lucky, the unexpected.
The learn-by-doing idea expressed by Norton reminds me so much of my own industrious, sea-loving boy. (Sometimes I wish school could be held on the beach!) Norton's book is my current read, and I am loving this memoir full of fascinating natural history and funny storytelling. (It is not a children's book, but check out the great cover.)
The mini-marine biologist at your house might like the early reader Tentacles!: Tales of the Giant Squid, written by Shirley Raye Redmond and illustrated by Bryn Barnard, and Sylvia A. Earle's non-fiction picture book Sea Critters, with beautiful close-up photographs (sea squirt, cuttlefish, cup coral, etc.) by Wolcott Henry. Sea Critters easily introduces a little scientific classification, too, using terms like Porifera (sponges) and Cnidaria (jellyfish & co.) in a context that children can understand.