Family of NYC fashion designer who died in Montauk yacht mystery claims owner caused her death, plans $50M lawsuit

The family of a Big Apple fashion designer mysteriously found dead in a swanky Montauk yacht club plans to file a bombshell lawsuit accusing a well-heeled investor of causing her demise, The Post exclusively learned.

The $50 million wrongful death suit by Martha Nolan-O’Slatarra’s family will be filed in Manhattan civil court, a filing Tuesday revealed — just one day before the anniversary of when the designer died on a boat docked in the club.

The family accuses the boat’s owner Christopher Durnan — an insurance mogul who invested in Nolan-O’Slatarra swimwear fashion company East x East — of causing her death through assault, negligence and gross negligence.

The court filing effectively announcing the lawsuit doesn’t detail specific accusations against Durnan, but contends in legalese that he “intentionally and wrongfully assaulted” Nolan-O’Slatarra.

Durnan is also accused of gross negligence and reckless and wanton conduct.

The alleged assault and negligence caused Nolan-O’Slatarra’s death either individually or in combination, the filing contends.

Police originally said they believed that Nolan-O’Slatarra died of an accidental drug overdose, but sources close to the family confirmed an independent autopsy found she only had “trace amounts of cocaine” in her system.

Instead, the independent autopsy found some form of assault led to Nolan-O’Slatarra’s death, sources said.

The accusations against Durnan add a new wrinkle to the still-murky circumstances behind Nolan-O’Slatarra’s death on Aug. 5, 2025.

A native of Ireland, Nolan-O’Slatarra, 33, moved to New York City a decade ago and quickly adopted a glamorous, jet-setting lifestyle.

She staked out a career as a fashion designer, hoping to find a foothold in the the affluent Hamptons.

Durnan entered Nolan-O’Slatarra’s orbit and invested in her swimwear brand, owning a 13% stake.

The insurance company owner — who was once sued for allegedly biting a retired FDNY firefighter on the 20th anniversary of 9/11 — was well-known in the area and owned a boat called the Ripple docked in the yacht club.

Nolan-O’Slatarra met with Durnan onboard the Ripple late Aug. 4, 2025, for a business meeting, according to New York magazine.

At one point, Nolan-O’Slatarra’s boyfriend and friends became worried she wasn’t answering any messages, with one hauntingly texting, “I’m sure her phone died. Or maybe she’s dead.”

The designer soon responded that she was at the yacht club, but roughly an hour later she died, police said.

She was found unconscious on the docked Ripple after residents nearby reported hearing screams late at night.

They were greeted by the sight of a naked man — Durnan, according to New York — who threw sunscreen at other boats to wake up sleeping boaters.

“Do something!” the naked man screamed, good Samaritans later told The Post.

Bystanders tried to resuscitate the Irish beauty but she was pronounced dead by first responders.

The shadowy circumstances behind Nolan-O’Slatarra’s death quickly drew attention, but Suffolk County cops were slow to provide answers.

Police denied multiple freedom of information requests from The Post for Nolan-O’Slatarra’s autopsy and other documents things related to her case as the investigation “remains open.”