A water-resistant cap by which, in use, can be secured in a stretched manner tightly around a user's head with maximal comfort during swimming and bathing, including (1) a dome-shaped main body enclosure with a crown providing ample housing to fit hair of any size, (2) the crown projecting downward to a perimeter edge extending about an aperture—with a front-edge section, right-edge section, left-edge section, and a rear-edge section—forming a comfortable, water-tight seal during swimming or bathing; and (3) an element projecting from an outer-surface of the dome-shaped main body enclosure in a seamless fashion; and a method of economically manufacturing such cap with a seamless element.