Jill Zarin shivers when she recalls the time she piloted her 50-foot luxury Sundancer — a $600,000 ride that husband Bobby bought her on a whim — on her maiden voyage. She says she was close to dying … and killing her six passengers, including socialite Denise Rich. “I could see the National Enquirer headline: ‘Denise Rich dies on Jill Zarin’s boat,’” Zarin, 50, says with a laugh.

After completing an eight-hour boating course for ladies, Zarin invited Rich and her other well-heeled friends for a day at the swanky beach bar Sunset Beach.

“I wanted to be a big shot and take them out to Sunset Beach for dinner,” says the former star of “Real Housewives of New York.”

While her guests were swimming around the boat, Zarin threw her line out, then mistakenly backed into it. Fifty feet of rope got caught in the propeller and disabled the engine completely, just as night settled in.

“At night, you can’t tell the water from the houses,” she says.

“It’s very disorienting and the tide was shifting fast — I thought we were going to crash into the rocks of Sunset Beach.

“The rope was so wrapped up in my propellers. It was easily $20,000 of damage.”

Zarin kept calm and sent out a distress call for help from Sea Tow, a 24/7 boating service.

“But the divers they sent were hot. The best thing about boating is the stories,” concludes Zarin, before cautioning would-be skippers with too much time and money on their hands: “Don’t get in over your head.”

That’s easier said than done, given the lax laws of New York state, which requires no boating license to operate a boat.

Zarin’s harrowing experience at sea is the tip of the iceberg for many wealthy weekenders from the city, who rarely drive a car — and yet think they’re the big fish out on the waters of the East End.

“The course of boating has changed drastically,” says Captain Joseph Frohnhoefer, a Sea Tow captain with 20 years of experience. (His dad founded the service on the East End 30 years ago.) Frohnhoefer has witnessed the East End evolve from serious local boaters to reckless weekend warriors.

“In the ’90s, you’d get a lot of nighttime calls, mechanical failures — people were more experienced and had more education,” he says.

“Nowadays, more people are getting into boating — they find themselves with money to get a boat, but don’t have the education [to operate it].

“There’s a lot more money than experience,” adds the captain, who has seen a 10 percent spike in distress calls to Sea Tow this season — from mechanical problems to slamming into rocks.

He says a total of 55 distress calls have been made so far in 2014 (up from 40 at the same time last year) — 90 percent of them from weekend warriors. Says one Sea Tow staffer: “This is unreal.”

Even curmudgeonly comedian Louis CK, who recently bought a posh pad on Shelter Island, has gotten in on the act, lamenting his first boating mishap and running aground on the Harlem River, stuck in mud for hours in his 42-foot yacht.

The trend is partly due to 1 percenters snapping up boats in record numbers.

“We’ve seen an increase in our higher-end boaters — high-end bow rider day boats and yachts — and that has to do with people buying real estate on the water,” says Matthew Levy, sales manager at Modern Yachts in Hampton Bays, who notes a big increase in new boaters in the past two years — one of whom just shelled out $320,000 for a “simple” 35-foot Sea Ray last week. “The sport-yacht market is very lively — obviously there’s a lot of wealthy people out here.”

The only ones benefiting from this phenomenon are the tow companies. Sea Tow, the longtime membership-based outfit, is used to bailing out hapless boaters. While annual membership dues are a nominal $169, those who don’t take precautions can end up paying considerably more: Hourly rates for towing and service start at $325.

And civility on the seas has given way to snootiness: “Boaters used to wave to each other — you just don’t see that anymore. A lot of normal common courtesy has left boating,” Frohnhoefer says.

But extant dangers worry the captain more than maritime courtesies.

“There are much bigger boats now, and they throw bigger wakes,” he says.

“A 50-foot boat blasting through is leaving a huge wake for small fishing boats, and it’s getting dangerous.”

Tom Connolly, a retired NYPD detective who now investigates boat accidents, has seen the swell of dimwitted seasonal folk who fancy themselves confident coxswains just because they can buy a yacht.

“They can afford these half-million-dollar boats — but they don’t know how to operate them,” says the Southampton resident, who’s been sailing since he was a kid. “My advice: Start small — with a 21-foot boat with some lessons for a few years — and work your way up. Don’t buy a 35-foot boat going 75 mph — you’re going to kill somebody,” he says, rolling his eyes as a half-million-dollar cigarette boat parked in the next slip revs its engine and stops everyone dead in their tracks.

“Any guy in that boat is a fat guy with a cigar,” Connolly snaps.

Jeffrey Reich, an East Side lawyer who summers in Westhampton Beach, always dreamed of conquering land and sea: “I had a little boating envy.” But in the two months he’s been on his new 21-foot speedboat, which can go 60 mph, the dad of two laughs off his maritime mediocrity.

“I’m having a hard time getting the hang of it. I’ve already been towed four times,” Reich admits.

The green captain, who is self-taught and doesn’t hold a boating license, should get used to having Sea Tow on speed dial.

“I’m a good customer — and I tip well! I want them to keep coming for me. My friend jokes, I should call them before we go out.”

Memorial Day weekend proved perilous for the new boat owner when he and his 10 passengers thought they were going to Dockers for lunch just a few minutes away, but choked on a sand dune instead after running aground, requiring another tow after being stranded for hours.

“It was like ‘Gilligan’s Island’ — it turned into a three-hour tour,” jokes Reich, whose Havanese has a more expensive life jacket ($80) than his teenage kids. “It’s been a comedy of errors — I’m learning as I go.”

And don’t get stalwart skippers started on boozy boaters.

In June, the Coast Guard announced more sobriety checkpoints around the region. If busted, BUI laws can be just as severe as DUI: A .08 BAC or higher can come with fines, jail time and a potentially revoked driver’s license, and offenders apprehended by the Coast Guard will be turned over to local law enforcement.

“The s–t show of all s–t shows in summer boating ridiculousness is Sunset Beach,” says Dustin Goodwin, a lifelong boater who regularly summers in the East End.

“Boaters go there, get blasted, and then have a boat they have to deal with.

“A guy I know had this huge sailboat and kept inviting women to go sailing on Sunset Beach,” says the IT professional from Park Slope.

“A bunch of random people would come on his boat, and he would party with them all afternoon.”

So how did the boozy boater with no regard for safety get back?

“Luck,” says Goodwin. “It takes a special kind of person who doesn’t go out with a GPS, hoping it will all work out.

“As a sailor, my version of Hamptons obnoxiousness on the water is getting too close to my boat,” he adds.

“They want to cut you off, they can be as obnoxious as they want to be. You’re a speck, and they’re on a giant yacht — and you be damned.”

And sometimes, you don’t even need to be in close proximity to cause mischief.

Fiona Kempton narrowly avoided disaster — and the next BP oil spill à la Hamptons — with a small gas and oil leak into the three-mile harbor. But the 37-year-old boating vet, a Red Hook handbag designer who summers in East Hampton, blames her newbie husband for her prized Columbia 30 sinking nose-first, causing thousands of dollars in damage.

“Here, any old cowboy can get a boat, but my husband never really had to take care of a boat,” she says.

Some locals aren’t surprised by the rate of near-disasters among the clueless captains.

“The best way to identify an idiot boater is how they anchor,” says Bill C., 56, a lifelong boater from Southampton who asked that his last name not be printed.

“What you have is people with a lot of money and no experience. Not a day goes by you see someone who doesn’t know what they’re doing,” he says.

“I told a guy today who pulled into the dock that it was a low tide, but he didn’t listen — and he banged up his boat!

“But this stuff takes years to learn — it’s not piloting a plane, but it’s harder than driving a car!”