Clark's account of her personal experiences with these vegetarian, aquatic mammals of the Florida waterways includes a brief history of the manatee and its relatives, information on current efforts to help these endangered animals, on their life cycle, and on their anatomy. While her prose is not always clear, her enthusiasm for the huge but gentle animals is evident: ""I later found out that manatees have six to seven molar teeth in each of four rows, two upper, two lower, that arise in the back of the jaw. These gradually move forward, and as they are worn down by chewing on the often sandy vegetation, they fall out and are replaced by new teeth."" Many of the underwater photos are murky green and gray, with the at-rest manatee a lump of light against the soft, fuzzy river bottom; they capture the spirit of these docile, do-little but endearing animals. Addresses for more information; index; illus. with photos.