A playful and picturesque beachside proposal took a terrible turn for the worse when the groom-to-be scooped up his new fiancée, tossed her over his shoulder and marched her into the surf — only to have her lose her brand new engagement ring.

It's a jewelry-industry truism that the exchange of diamond jewelry should never take place in or around large bodies of water.

Unfortunately, 24-year-old Katie Nicholson (a fitness influencer known as Beast Barbie) and her now-fiancé Steven Frank had to learn this the hard way.

In social media posts that have been viewed more than a half million times, Nicolson described a proposal that quickly transitioned from elation to desperation.

Frank, who owns Beast Elite Training in Bedford, IN, was enjoying the Fourth of July holiday weekend with Nicholson at an ocean beach when he got down on one knee and surprised his girlfriend with a princess-cut diamond engagement ring. She said, "Yes," to Frank's proposal and the couple embraced.

Outfitted in a white sundress, Nicolson proudly showed off the ring in a photo shared on her TikTok and Instagram pages.

But then Frank, dressed in beige slacks and a white dress shirt, took Nicholson for an unscripted dip in the ocean. They disappeared under the waves, and when they emerged, Nicholson noticed that her ring was gone.

"Wait the ring," she titled one of the photos showing her and her fiancé digging through the sand in a hopeless attempt to retrieve the ring in knee-deep water.

The next photo shows how the scene has grown more intense as many passersby join to help in the search.

"There's no way we're finding it," read her next caption. "It’s in the OCEAN.”

But in the final frame, Nicholson reveals that the ring was found by one of the Good Samaritans. She simply calls him "Miracle Guy."

"& now we have the craziest engagement story to tell," Nicholson wrote in a social media post punctuated by a Grinning Face With Sweat emoji, a Grinning Face with Tears of Joy emoji and a Loudly Crying Face emoji. "This was quite the emotional roller coaster but I think we’re meant to be together."

On Instagram, she wrote, "My forever. How lucky am I to get to spend it with my best friend & the most amazing man. I’m so excited for this next chapter with you."

Credits: Screen captures via Instagram / beastbarbie_ and stevenfrank3_.