Lindsay Hubbard and Carl Radke Are Engaged! Inside the Summer House Couple's Romantic Proposal

Lindsay Hubbard and Carl Radke are taking the next step in their relationship — one down the aisle!

The Summer House stars got engaged on Saturday, PEOPLE can exclusively reveal, in a romantic private proposal at Southhampton's Dune Beach captured by the Bravo cameras for the reality show's upcoming seventh season.

"I was so surprised, I'm still in shock!" Hubbard says, Radke admitting, "It was quite the whirlwind throwing off Lindsay. She's a tough one to catch off guard!"

For the big moment, the sales executive convinced Hubbard the two were heading to a group bonfire and had to arrive early with firewood to set up. Instead, she was greeted with an intimate picnic for the two of them. "I got there and was like, 'Umm, I'm starting to think we're not having a bonfire," Hubbard recalls with a laugh.

Walking from the boardwalk to the beach, Radke even laid out signs with messages like "7 Years" (a reference to how long they've known one another) and "Best Friends." He also included lyrics to Lee Brice's "Rumor" and REO Speedwagon's "Can't Fight This Feeling" — two songs with special meaning for the pair.

Adam Szulewski, Olga Lezhepekova

"As we got there, I told her, 'We haven't had time to have alone time this summer, and I wanted to do something special,' " says Radke. "And I had the ring in a beach bag that she was carrying that I snuck in there. And she turned her back, and I figured, 'This is my chance' and I grabbed the ring, got down on one knee, and I turned her around and told her I wanted to spend the rest of my life with her, how happy I was, and that our love story was just beginning."

"He said, 'Will you marry me?' and I said, 'A thousand times, yes!'" Hubbard gushes. "And he said, 'Hold on, let me get the ring' and I was like, 'I don't care! When should we get married? Now? I'm ready!'"

Adam Szulewski, Olga Lezhepekova

That ring, however, was pretty special. Radke popped the question with a sparkling Nicole Rose ring featuring a 3.5-carat square brilliant cut cushion with two half-moon diamonds on the side (making the ring 4.02 carats total).

"This is the most incredible thing I have ever laid eyes on, except Carl," Hubbard tells PEOPLE. "I don't think I slept at all last night, I think I just stared at this ring. It's gorgeous. He really crushed it, it could not have been more perfect."

"I like to think that I'm pretty good at knowing what Lindsay likes, but I did have some help from Nicole Rose, who is an incredible jeweler and good friend of Lindsay's," Radke says. "I had picked up on a couple of things Lindsay liked and Nicole helped me narrow it down to a few stones, sent me design ideas, and created this beautiful ring."

RELATED: The Celebrity Engagements of 2022

Both note the sentimental value attached to the ring.

"I'm really happy with how it turned out," Radke adds. "She means everything to me, and I wanted it to be something that was reflective of my love for her and how excited I am to take the next step."

"It's a whole lot of love," Hubbard says. "It's very clear, if you look at this finger, that this man loves me so much."

Adam Szulewski, Olga Lezhepekova

Afterward, the pair went to Dockers Waterside Marina & Restaurant — one of their favorite places — where their engagement was celebrated by friends and family, including Hubbard's dad and step-mother, who flew in from Florida for their first visit to the Hamptons.

"That's when it all became real to me," Hubbard said. "Until that point, I was like, 'Is this happening right now?' But when I saw my parents and some of my best friends who don't even live in New York who had flown in, I knew it wasn't just a dream. And I just lost it. I lost it. I started hysterically crying."

"She kept saying, 'Should I call my parents?' — not knowing that they were also waiting for her. And I was like, 'The service is spotty here, let's just wait until we get to Dockers,' knowing the next level of the surprise."

Their Summer House costars were there too, including Kyle Cooke, Danielle Olivera, Paige DeSorbo and Mya Allen. "They were all surprised too because the entire house didn't know it was happening — they also thought they were going to a bonfire," Hubbard says. "Amanda [Batula] even missed it because she was back in New York City, taking care of her dogs who just got spayed. But Kyle FaceTimed her, and we got to say hello."

"We're going to do another engagement party in New York in a few weeks," Radke says, noting the party will be a chance for his mom and other friends who couldn't make it to celebrate with them. "I tried to get [Summer House alum] Luke Gulbranson out last night, but he was in Minnesota. But Andrea Salerno and his girlfriend Lexi happened to be in town, so they got to be there, which was really cool."

Lindsay Hubbard Instagram

Hubbard, 36, and Radke, 37, have starred on Summer House since its premiere in 2017.

They've known one another for seven years and built a best friendship over the years. Romance blossomed for them last October, the two broaching the subject at Cooke and Batula's wedding on the season 6 finale of Summer House.

They confirmed their relationship to the public in January, though their status as an official couple was news to Hubbard. "I found out we were boyfriend and girlfriend when he went on Watch What Happens Live in January," she recalled to PEOPLE in May. "We hadn't even had that conversation together yet, but I think we both knew how serious we felt about one another that neither of us really needed to discuss it. We were both on the same page."

RELATED: Lindsay Hubbard Reveals She and Carl Radke Are Moving in Together: 'New Chapter'

"We're lucky because the universe came together, and the timing worked out!" Hubbard said. "I don't think I've ever been in a healthier relationship. Falling in love with your best friend, I don't think there's any better feeling in the world."

Jamie McCarthy/Getty

In fact, Hubbard said both were so happy together that they would have confirmed they were dating to inquiring fans on social media earlier, but they wanted to just enjoy the early days of their pairing.

"It was those butterflies, that honeymoon phase that people on reality TV don't often get to enjoy," Hubbard said. "We really protected that time together that we had, getting to know each other in that dynamic. It was just so fun and exciting."

"We really enjoy spending time together," she continued. "We never get sick of each other. You know there's those relationships where you need your space, your alone time, your separation? Carl and I are the opposite of that. We really enjoy doing everything together. We work out together, we each lunch together. He's my best friend."

RELATED: Summer House's Lindsay Hubbard Reveals "Where It All Started" in Her Romance with Carl Radke

This wasn't the first time the two had dated, though an attempt three years earlier didn't work out. "The timing wasn't good for either of us," Hubbard said. "[But] we got stronger as friends after that and then progressively got closer and closer and closer until eventually we started dating."

Rich Polk/Getty

Since then, the pair haven't been shy about professing their love for one another on social media. They even moved into a new two-bedroom New York City apartment together in June.

He was also "a rock" for Hubbard, she said, during her egg-freezing process. "He was amazing and so, so sweet. He took me to acupuncture to help relieve any stress and tension ... and took me to my actual procedure, brought me home. ... He also booked us a night at the spa after my [egg] retrieval, where he got us massages. He's been extremely, extremely supportive."

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.

As for this next chapter, Hubbard and Radke tell PEOPLE on Sunday that they're keeping the wedding plans and the baby plans open.

"I am very much of the mindset of, whichever way the universe wants to go with our timeline, I'll follow," Hubbard says. "I threw my own timelines out the door, they do not exist. Whether a wedding or marriage comes first or a baby, it doesn't matter. This is my life partner; we want all the same things together."

Season 7 of Summer House is expected to premiere early next year.