"I found the strangest things, from a case of oranges to funny little figurines covered with languages I couldn't read. It was nuts," Underwood told Business Insider.
Underwood - who has documented the aftermath of the nuclear disaster at Chernobyl - thought about heading back out to the park to photograph the devastation. But then he decided he didn't just want to take pictures of the trash. He wanted to transform it.
The process of collecting, building, and photographing is both "physically and mentally exhausting," Underwood says.
Underwood pursues this tiring project because he wants to start a conversation with Houston residents about the pollution in their backyard. That pollution may be more obvious to Underwood - who grew up in the woods of Missouri - than it is to people who have lived their entire lives in Houston.
While he generally leaves the sculptures on the beach for others to view and respond to, buildings and galleries have approached him and asked if they could show his work. He's skeptical about moving his sculptures indoors, though.
"These sculptures are nasty and messy," says Underwood. "They are covered in oil stains, bugs, and stuff that you don't even know what it is."