4 years ago, Priscilla Cummings came to my school, with tons of books that she would autograph for us (mine reads "For Tasha - Happy Reading! Priscilla Cummings 2006"). The one I bought was Chadwick the Crab. It is a terrific book that takes place right in my very own Chesapeake Bay (I live in Maryland [in fact, it was published by Tidewater Publishers, right in Centreville, MD. My school was in Centreville, Maryland. How kool!]).
I would reccomend this book for 4-6th graders. A great tale of a crab (Chadwick, obviously) who has a dream bigger than his little Chesapeake Bay life. Dreaming of being in the aqaurium, so he doesn't have to sleep all winter, he travels to the Balitmore Aquarium where he sucessfully spends the rest of his life as an aqaurium movie star.