Ms. Thomas started out with about 20 pieces, including swimsuits, cover-ups and jackets, custom made with beaded and sequined fabric like organza and toile. Then, they are adorned by hand-sewn appliqués, crystals, taffeta, and trim. Depending on style and craftsmanship, tops can cost $600 to $800, bottoms from $550 to $800, and one pieces around $1,300 to $2,000. Full-length cover-ups can start at $1,800 and go as high as $7,000.

“We have a rose coat with 200 organza and toile roses,” she said of a jacket that costs $6,000. “I didn’t want to be a middle market brand.” She said she is also looking into eventually offering plus-size pieces.

Ms. Sabag, who lives in Roslyn, N.Y., started Karen Sabag Bridal, in 2008, offering handcrafted, atelier dresses. Her designs range in price from $10,000 to $30,000 and beyond. Over the last several years, “more brides were asking for swimsuits,” she said.

In November 2020, she created Rêver (which means dream in French), specializing in custom, hand-embellished swimsuits and lingerie. This summer, she will open her first Rêver flagship store in Gravesend, Brooklyn, offering 18 swimsuit styles and 40 interchangeable items, including cover tops, overlays and lingerie. Like Ms. Thomas, Ms. Sabag uses imported Chantilly and beaded lace, delicate silks, pearls, stones, embroidery and corsetry.