In the 1880s, people used wheeled shacks called “bathing machines” to give themselves a private enclosure at the beach. Now there's a more compact option: the changing robe, also known as the surf poncho.
As the latter name makes clear, these were originally pioneered by surfers. A pain point often faced by surfers is getting changed in the parking lot or on the beach. Surf ponchos act as a towel, wind-braker, and privacy shield while getting into and out a wetsuit.
Social media can help to dampen the otherwise turbulent ride of selling highly seasonal products like swimwear. On Instagram, summer is year-round: since winter in the Northern Hemisphere is summer in the Southern, posts from Australia, Africa, and South America infiltrate new feeds while the US is in winter, which makes summer gear easier to market for holiday purchases.
This outfit has a paradoxical relationship with privacy: changing robes are often brightly colored, and they're a large, attention-grabbing garment. Since they’re so visible, they end up promoting the product in person and online merely by being a high-visibility billboard for the changing robe concept. So they create an oasis of privacy even though they grab people's attention—and a marketing channel, too.