Hawaiian petroglyphs dating back at least a half-millennium are visible on Oahu for the first time in years, thanks to seasonal ocean swells that peel away sand covering a panel of more than two dozen images of mostly human-looking stick figures, El.kz cites AP News.

The petroglyphs are easy to spot during low tide when gentle waves ebb and flow over slippery, neon-green algae growing on a stretch of sandstone. This is the first time the entire panel of petroglyphs are visible since they were first spotted nine years ago by two guests staying at a bayside U.S. Army recreation center in Waianae, about an hour’s drive from Honolulu.

Native Hawaiian cultural practitioner Glen Kila, who traces his lineage to the aboriginal families of this coastal Hawaii community, said he believes the resurfacing of the traditional marvels are his ancestors sending a message.

“It’s telling the community that the ocean is rising,” said Kila, a recognized expert on the local culture and history of Waianae who is consulting with the Army on the protection of the petroglyphs.

Army officials are trying to balance protecting the petroglyphs with their accessibility on a public beach.

John and Sandy Stone consulted tide charts and drove about 30 minutes from their home early Tuesday to get a glimpse after a watching a local TV report about the petroglyphs.

“It was so interesting to touch them,” said John Stone, who splits his time between Hawaii and California. “It felt interesting to kind of have a connection with the past like that.”

It is difficult to date petroglyphs, but an archaeological site in the area is from about 600 years ago, said Laura Gilda, an archaeologist with U.S. Army Garrison Hawaii. According to Kila, Hawaiians arrived in Waianae at least 1,000 years ago.