Mayor Bill de Blasio marked the start of summer Saturday by marching in the Coney Island Mermaid Parade bedecked in a pirate costume, his wife, Chirlane McCray, in an electric-blue dress and wig and teenage children covered in body paint.

Dante and Chiara de Blasio were the 32nd annual parade's Queen Mermaid and King Neptune. They wended their way about a mile and a half along Surf Avenue and onto the boardwalk, met with cheers and screams and the ocean breeze.

"I want you to look for the tallest pirate you've ever seen," an announcer shouted from the reviewing stand. "That would be the mayor." There was de Blasio, having donned a pirate's hat, breeches and sword.

The first children were being wheeled in front in a rickshaw, or "ocean rolling chair."

Tens of thousands jostled to cheer and snap pictures of the first family, with just one audible boo, from a shirtless man unhappy with de Blasio's stance against Central Park hansom cabs.

De Blasio's children had their latest starring role in his political life, after prominence in TV ads during last year's campaign, which spotlighted his diverse family and boosted his candidacy.

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One of the de Blasio fans Saturday was 65-year-old Maria Ramos of Canarsie, who waved the rainbow flag, the symbol of the LGBT rights movement, in honor of her gay son.

"I love that you love this flag," she shouted. De Blasio turned and blew a kiss her way.

At the end of their route, de Blasio and his high-school-age son got into a play fight -- the mayor with his sword, Dante with his trident.

"We have become friends now," de Blasio joked after they called it a draw.