The eggs hatch in about ten days, but platypus infants are the size of lima beans and totally helpless. Females nurse their young for three to four months until the babies can swim on their own. A full grown Platypuses range in length from 38 to 60 cm (15 to 24 inches) males are generally larger than females. Aquatic adaptations include the flat streamlined body, dorsally placed eyes and nostrils, and dense waterproof fur that keeps the platypus well insulated.