The last person authorities believe may have seen Sudiksha Konanki, the 20-year-old University of Pittsburgh student who vanished while on a spring break trip in the Dominican Republic, was back on the beach — this time with investigators.

In the early morning hours March 16, Joshua Riibe, 22, walked with Dominican Republic investigators on the beach where Konanki was last seen March 6.

Hours before walking the beach with investigators, Riibe exclusively told NBC News, “I’m just trying to help them out.”

“The ocean is a dangerous place,” he added.

Riibe was named as a person of interest by the Loudoun County Sheriff’s Office in Virginia, but the office has no jurisdiction over the case. Authorities in the Dominican Republic have said that nobody is considered a suspect yet and that they do not use the term “person of interest.”

Riibe told local authorities that he had rescued Konanki from drowning before she went missing in Punta Cana, according to a transcript of the interview obtained by NBC News.

During a March 12 interview, Riibe told investigators that he and Konanki, who was last seen around 4:15 a.m. on March 6, were together before she disappeared. He said that while they were at the beach, the two were “in waist-deep water, talking and kissing a little” when a wave crashed into them and took them “out to sea.”

“I tried to make sure she could breathe every moment, but that didn’t allow me to breathe all the time, and I swallowed a lot of water,” he said.

He said that he was able to get the two of them back to shore, but they remained in knee-deep water.

“I asked if she was OK. I didn’t hear her answer because I started vomiting all the seawater I’d swallowed,” he said. “After vomiting, I looked around and didn’t see anyone. I thought she’d grabbed her things and left.”

In the interview, he said he was surprised to learn she didn't return to her room.

Riibe is a student at Minnesota's St. Cloud State University. The law firm representing Riibe told NBC News via email that Riibe's passport was confiscated as part of the investigation. Prosecutors in the Dominican Republic would not confirm to NBC News if Riibe's passport had been confiscated.

The firm said that Riibe “has been confined to the hotel since the investigation began” and “is permanently escorted by the police anywhere he goes.”

The U.S. State Department and the Dominican authorities have not confirmed if Riibe is officially being detained.

Since the disappearance, international authorities have led a search for Konanki. Local emergency operations agency La Altagracia Civil Defense said in a statement on Facebook that it would be coordinating an extensive search for the student.

In a statement translated by TODAY.com, the Dominican National Police said on March 9 that surveillance footage was obtained of Konanki and her friends from the night she went missing.

The video showed Konanki walking with a group of people to the beach area at the hotel. Local investigators said that her friends returned to the hotel around 40 minutes after they went to the beach, believing that she stayed behind with at least one person.

Loudoun County Sheriff Michael Chapman told NBC Washington that Konanki remained on the beach with people who weren’t from her college that she met on the trip.

Chapman previously told NBC News, “We don’t really have any idea exactly what happened after that ... when her friends returned back, and she didn’t.”

At this time, Konanki’s disappearance is still being investigated as a missing persons case.