Researchers say the new hole at Mt. Baldy is similar to the one that swallowed Nathan Woessner.
It's a beautiful Summer day at the Indiana Dunes, but there's cause for concern.
"You expect to enjoy one nice day and something bad can happen," said Roger Robey, beachgoer.
"It sounds pretty freaky to me," said Essi Ala-Kokko, beachgoer.
Freaky, because a government surveillance crew discovered a second hole at Mt. Baldy this week.
"The fact that we found a second one in Mt. Baldy makes us wonder what exactly is, perhaps, unique about Mt. Baldy-- what's going on under there that is causing these holes to show up?" said Bruce Rowe, Supervisory Park Ranger, National Park Service.
The first hole swallowed up 6 -year-old Nathan Woessner last month, triggering a massive rescue effort.
He recovered after being buried nearly 4 hours. On Wednesday, his dad was surprised about the second hole and wants the area to be safe for others.
"I'm more relieved that they have found something in addition to all of this. Hopefully it has helped and maybe saved a life or two," said Greg Woessner, Nathan's father.
Park officials say the second hole is 5 feet deep, and 10 inches in diameter. And there is a leading theory for both holes.
"That is was a tree long buried under Mt. Baldy. That it rotted out, most of the tree trunk was gone, perhaps almost all of it, but the hole was left behind where the trunk had been," said Rowe.
In the meantime, beachgoers are leary.
"Pretty scary situation, if it happened once, it wasn't a fluke," said Romie Dybas, beachgoer.
And they're raising questions...
"Who knows. . . maybe there is a third and a fourth!" said John Rukavina, beachgoer.
For now, Mount Baldy will remain closed to the public.
