SAN DIEGO — Less than a year after SeaWorld debuted its signature submarine ride within the San Diego park’s new Ocean Explorer attraction, the ride has been shut down for months with little explanation.

Submarine Quest, which SeaWorld boasted would transform visitors into underwater researchers, opened last June but following the summer season was rarely open and has not been operating this year, with no explanation given of when — or whether — it will reopen.

References to the three-minute-long ride, which ran along an elevated track, are no longer on SeaWorld San Diego’s website where it showcases its attractions, and there is no park signage offering an explanation for the closure. And the entrance to the ride has been cordoned off to the public.

SeaWorld officials would provide no details on reasons for the closure, only saying that the park is working through technical issues.

“As we’ve conveyed to our park guests who’ve asked, the Submarine Quest ride at Ocean Explorer is currently undergoing maintenance,” SeaWorld San Diego spokesman David Koontz said in an email to The San Diego Union-Tribune. “As soon as there’s additional information, we will communicate that to you and our guests.”

The ride, though, has been closed since at least January, opening only temporarily last December after the summer season, and since then, regular parkgoers say they have not seen evidence of work being performed on the ride.

Submarine Quest, designed for younger children, was introduced as part of Ocean Explorer, a two-phase attraction that initially opened in 2017 as a combination of aquariums and multiple kids’ rides, culminating with the May debut of Electric Eel, the park’s highest, fastest roller coaster.

The individual submarine vehicles were outfitted with interactive digital navigation dashboards meant to replicate the experience of a deep sea explorer on a mission. The very short, dark-ride portion of Submarine Quest brought riders face to face with a huge digital eel.

Hastin Zylstra, a self-described theme park geek and regular visitor to SeaWorld, has tracked the ups and downs of Submarine Quest via his visits to the park and social media and says there have been no recent indications of maintenance work or a reopening timeline for the ride.

He pointed to a Tweet last September from a frequent visitor, who said, “SeaWorld will Submarine Quest ever be fixed? 4th visit to the park since the grand opening and it has not once been operational??”

Said Zylstra, “Given that they spent most of 2017 trying to get it open, it then opening to lackluster reviews, and now that Electric Eel has the marketing spotlight, I can’t imagine they are going to spend any more money on it. It’s just unfortunate for SeaWorld, given the company’s current situation, that they are going to have a ‘standing but not operating’ ride in one of their flagship parks.”

In recent years, the San Diego park has struggled to reverse declining attendance, fueled in part by the backlash from “Blackfish,” the 2013 anti-captivity film that focused on SeaWorld’s treatment of its killer whales.

Once Ocean Explorer opened last year, the feedback about the ride from theme park bloggers and amusement park enthusiasts was largely lukewarm to negative, unlike the reviews of Electric Eel, which has generally been widely praised.

In an earnings call last year, former SeaWorld Entertainment CEO Joel Manby, who suddenly left the company earlier this year, acknowledged that Ocean Explorer had fallen short of expectations and hadn’t delivered the return on investment that was anticipated.

Shortly after Manby’s resignation in March, SeaWorld announced that two of its top executives in the design arena — Anthony Esparza, chief creative officer, and Brian Morrow, vice president of theme park experience design — were stepping down.

Morrow, who has since formed his own production company, declined an interview request about the SeaWorld attraction.

Adding to the mystery surrounding Submarine Quest, Screamscape, an online guide to theme parks, posted a news item May 16 suggesting that the ride may not reopen:

“(5/16/18) While the Submarine Quest has been closed perhaps longer than it was ever open, a reader noticed that any and all mentions of it have now been removed from the park’s website as well. When sending in a question to the park about the ride’s status, they were told that it was, ‘closed indefinitely.’ No telling if they will ever reopen it, or if it is destined for the scrap pile.”

Theme park consultant Dennis Speigel said he was skeptical that the closure of Submarine Quest was driven solely by operational issues.

“I heard that it was closed because the attraction was way far less than what SeaWorld had envisioned it to be when they commissioned it and that they didn’t feel that it justified keeping it open to the public,” said Speigel, president of International Theme Park Services. “It just didn’t have the story and the guts it needed to entertain and interest the visitor.”