A soon-to-be-married San Diego couple had a surprise guest in their engagement photos — and it's sure to have them cracking up for years to come

When a soon-to-be-married couple decided on a nearby San Diego beach for their engagement photo shoot, they didn’t anticipate that the images would provide a lifetime of laughter.

On March 14, Amy Sefton and her fiancé Jake, both 26, walked to San Elijo State Beach, which is close to her apartment, with their photographer, Austin Whitesell, to capture photos for their wedding invitations.

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“We didn’t have a ton of time for the shoot. It was after work. I wanted somewhere pretty, but we couldn’t travel very far before the sunset. I was like, ‘Well, this is right across the street from our house and also Jake proposed right there, so we can probably go back to the same spot since this area means a lot to us,’ ” Sefton, who works in the technology industry, tells PEOPLE. “And we could walk, so it was easy.”

Image zoom Austin Whitesell

But while the lovebirds were holding hands and posing for the sunset photo session, a surprise (and shocking) visitor was captured in the background of their images: an elderly gentleman wearing a white G-string.

“It’s a nice, fun, family-friendly beach. In this photo it’s just the naked guy, nobody else, but the opposite direction there were tons of families and kids around on the beach. It’s totally not a nude beach,” says Sefton. “Actually, our photographer … he was like, ‘Um, is this a nude beach, guys?’ We’re like, ‘No.’ ”

Adds Jake of the moment when they first noticed the nearly naked man, “We’re like, ‘What? No.’ He’s like, ‘Turn around.’ And so we turn around and look.”

At first glance, Sefton was shocked. “I was like, ‘Eww,’ and then I started laughing. I was like, ‘What the frick? There’s kids around.’ But then I was like, ‘Oh, this is actually pretty hilarious!’ ”

Image zoom Austin Whitesell

Similarly, Jake had to do a double take of the moment.

“At first, I was like, ‘I don’t want to see that.’ And then I had to make sure what I saw was actually a nude dude walking on the beach. Where we were looking, there’s a bunch of kids playing and I immediately looked back over to them,” he recalls. “I was like, ‘Oh my gosh, those poor parents. Those poor kids.’ ”

While some may have chosen to wait until the unclothed photobomber was out of sight to continue with the photo session, Whitesell capitalized on the hilarious moment.

“At first, I was trying to remember if I took the couple to a nude beach by accident. It wasn’t my intention and luckily the couple I was shooting did not see him, as they were too busy looking at each other,” says Whitesell. “However, I saw the opportunity when he walked past me and into the shot.”

“He was like, ‘Yeah, this is too funny not to capture it,’ ” Jake recalls.

Whitesell explains that he “asked them to lean back a bit” so that he could snap the moment, which he describes as “comical, random and very California.”

“Then I shifted my lens to an angle where he ended up being right in between them,” he adds. “I figured they would laugh about it after I took the shot, even though they were confused at first.”

In the set of images, the mystery man is flanked by the couple as he walks the opposite direction, and his bare buttcheeks are at the center of the shot. Although it requires the squinting of eyes to see the man’s white G-string, the couple assures PEOPLE that he was not nude on the public beach.

“But if you zoom in on the photo, he’s got this like little white G-string thing that’s just covering up barely in the front. I mean, pretty much he looked fully naked. So I guess technically it wasn’t illegal because it’s not a nude beach,” says Sefton. “Whatever he was wearing was practically the same color as his skin. We just looked and we’re like, ‘Whoa!’ and looked away. We were cracking up and our photographer’s like, ‘Okay, we gotta get a good photo of this!’ ”

Image zoom Austin Whitesell

Adds Jake: “Even if you look at his front side, your eyeballs really have to be looking for his junk to notice whether or not he was wearing something.”

Although the mystery man didn’t know the pair, he also realized the hilarity of the moment.

“He looked at us and he started laughing, I think because he saw how ironic it was,” shares the bride-to-be. “We’re a couple dressed up nice taking engagement photos and he’s just practically nude walking through our photos.”

And while the location is now filled with comical memories for the couple, who will tie the knot in June, it is also the same place where two milestones moments in their relationship took place.