Flannel is the best material for a bathing costume, and gray is regarded as the most suitable color. It may be trimmed with bright worsted braid. The best form is the loose sacque, or the yoke waist, both of them to be belted in, and falling about midway between the knee and the ankle; an oilskin cap to protect the hair from the water, and merino socks to match the dress, complete the costume.
John H. Young, Our Deportment
Hit the beach 1880s-style! Swaddled in a gray flannel sack, oilskin cap, and merino socks, you’ll avoid sunburn. The only drawback is that other swimmers may mistake you for a walrus.