Being swallowed by a sinkhole may not have been at the top of your list of fears, but this video is terrifying.

Last Friday, a couple exiting a bus in Seoul plummeted 10 feet into the sidewalk when a sinkhole opened beneath their feet. The incident was caught on the bus’s surveillance video and spread across social media sites.

According to UPI, the incident happened near the Yongsan rail station. Firefighters rescued the couple, who walked away without serious injuries.

“Looking at the actual sinkhole site, the key point is that water is coming out of the retaining wall,” Cho Seong-ha of the Korean Geotechnical Society told Sky News. Seoul and the Korean Geotechnical Society are investigating the cause of the sinkhole, Cho said, as the cause is still not known.

“We are planning to analyze the possibility through investigation,” Cho said. “We are also planning to figure out other causes for the sinking by looking at various construction records and by investigating the site.”