Vogue finalist designer Thaddeus O’Neil debuts surfer line on Amazon's 'The Fashion Fund'

No pressure — you’ve got 15 minutes to describe past work, current business and future plans, hopes, dreams. The clock is ticking. Go!

That was the first of several challenges for rising-star fashion designer Thaddeus O’Neil, a Brookhaven native and avid surfer and a finalist for the CFDA/Vogue Fashion Fund award. O’Neil has survived fierce waves and frigid temps in the churning waters around Montauk, Smith Point and Long Beach — but this was like paddling through a tidal wave of anxiety.

“Imagine presenting to some of the most important people in American fashion — and Anna, one of the most important in the world,” says O’Neil.

That’s Anna, as in Anna Wintour, sunglassed Vogue editor and artistic director of the Condé Nast publishing empire, one of 10 judges (including fashion legend Diane von Furstenberg) who reviewed hundreds of applicants before selecting 10 finalists, a grueling process chronicled on Amazon’s reality series “The Fashion Fund.” It debuted Feb. 25, with a new episode streaming every Thursday — for free. (It’s not behind Amazon Prime’s subscription wall.)

Now in its third season, the 10-part series has a lot at stake — the winner gets a six-figure check, and a year of mentoring from industry vets. This is where hotshot designers like Alexander Wang, Billy Reid and Tabitha Simmons got their start. The winner was announced last November, but, despite not getting the big prize, O’Neil was upbeat about the experience and excited about the future.

With his sun-streaked blonde hair, tank tops and perennial tan, O’Neil is arguably — of all the finalists and brands — the best spokesmodel for his own eponymous label, a line of surf-inspired menswear he describes as “beachy and loose and effortless.”

The brand’s dapper-surfer-dude vibe owes much to his years spent on Long Island. O’Neil, 40, grew up in Brookhaven hamlet, attending Bellport High School, then Colgate University in upstate Hamilton, returning for a master’s in philosophy at Stony Brook University.

Fashion found him as a boy, when famed photographer (and neighbor) Bruce Weber began photographing O’Neil’s dad, a local clammer, and the family.

As a kid with style on the brain, he insisted mom photograph his “outfit of the day” — apparently inventing the whole “OOTD” trend long before it was a hashtag. He raided his mom’s and sister’s closets, pilfering sweaters and jeans if they had a cool fit. Sis wasn’t pleased but mom didn’t mind — till he cut up her jeans to alter them.

“I had no boundaries,” he says, smiling.

Now living in Manhattan’s East Village, O’Neil keeps a cottage in Brookhaven. “Thanks to the federal wildlife preserve,” he says. “you go down the beach and you’re in a very remote-feeling place.”

In episode three, you see him in his element, on Carmans River in Brookhaven, with his wife, Australian model Pania Rose, and their cherubic 3-year-old son, Cassius. Yeah, you may want to toss him in the drink — it looks the picture-perfect life.

Today, walk up the five rickety flights to his sunny new Chinatown studio, still under construction, and you’ll find him, amid lumber, design tables and racks of clothes, planning his next collection. Urged on by Wintour, he’s expanding into womenswear, which, to him, is like growing the family.

“I had two babies at once,” he says. “I started my brand in 2013 when my son was born. That’s the best way it could’ve happened. You realize what’s important. It keeps you grounded.”

Call that surfer wisdom. After all, if you’re doing it right, even the gnarliest wave brings you back to shore.