When 2nd grade teacher Hannah Roddy filmed her colleague recording a virtual math lesson dressed as a shark, she never imagined the response.

"I posted it on TikTok toward the end of the day and by the time I drove home, which takes about 30 minutes, it had 10,000 views," Roddy told "GMA."

Now, nearly 20 million people have watched Skitcha Elementary 2nd grade teacher Ashlee Skelton teach and dance to "Baby Shark."

VIDEO: 20 million people have watched this teacher's 'Baby Shark' math lesson
"This is what teaching is."

"I heard the song through the wall and I thought 'this is hilarious,'" Roddy said.

As funny as the video is, Roddy pointed out this is "just a glimpse behind the scenes."

"This is what teaching is," she explained. "We do this kind of stuff every day."

Skelton told Roddy that when the video played on her students' Zoom, she thought she saw some of them "cringe."

Even though the song might not be a favorite, Roddy said the parents and school have been "very supportive."