A family fishing in Maryland spotted a rare whale shark during a Fourth of July outing, the second such sighting in less than a month.

Josh Schleupner told DelmarvaNow that he and his family were on the "Moore Bills" boat fishing in Ocean City on Tuesday when they saw the sea creature. He added that it was a slow fishing day out in the ocean, having no luck reeling in tuna.

But then a whale shark -- which can weigh up to 20 tons -- came right up to Schleupner's boat, leaving everyone on board in awe. Schleupner's stepson jumped into the water to try to touch the creature, but it swam away.

Moments later, the whale shark came back around and Schleupner seized the moment, according to DelmarvaNow. After getting an OK from the boat captain, he threw his mask on and jumped in.

"It was a once-in-a-lifetime opportunity. I dive, but never in 100 years did I think I’d be able to swim with one, much less right off Ocean City," Schleupner told the news site.

"It was definitely worth it to get that close to him; to one of God’s creatures that are that big," he said, adding that he "swam like hell" to reach the whale shark.

This was the second sighting of a whale shark in Ocean City in less than a month. On June 27, Steve Moore also got a glimpse of the massive sea creature.

"We were on an overnight trip and my mate was taking watch during the night," Moore said. "He woke me up saying I had to see something, that a huge whale shark came up on the boat. I looked out the port window and it was right there, practically rubbing his nose up against the boat."

Moore described the whale shark he saw as being about as long as 40 feet.

Whale sharks are the largest living vertebrates and can grow up to 20 tons and 32-feet long, according to National Geographic. The creatures can live more than 70 years.

Ryan Taylor, a professor of biology at Salisbury University, told DelmarvaNow that despite having "shark" in their names, whale sharks aren't interested in biting humans and are generally docile.

He added that whale sharks are rare to find in waters off the coast of Delaware and Maryland.