A pair of Houston, Texas, teenagers caught an impressive sea creature while fishing on Friday: a gargantuan alligator gar that measured nearly seven feet in length.

The alligator gar is a species of fish that traces back 100 million years, reported the U.S. Fish and Wildlife Service's Fish and Aquatic Conservation. As such, they are sometimes referred to as "living fossils."

Members of the species typically weigh between 100 and 160 pounds and can measure four to six feet in length. However, at their largest, alligator gars can weigh up to 350 pounds and grow up to 10 feet long.

High school seniors Charlie Oliver and Evan Adams, both 18 years old, were fishing at Houston's Buffalo Bayou on Sunday when they encountered the massive fish.

However, when Oliver first sensed something large on his line, he thought he had come across an alligator snapping turtle, reported Chron.com. For context, alligator snapping turtles are the largest species of freshwater turtles, with males usually weighing between 155 and 175 pounds.

"We catch really big alligator snapping turtles on accident all the time, so I thought that's what it was," said Oliver, according to the news outlet. "The turtles kind of stick to the bottom and just feel really heavy on the line, but a little bit into the fight, we realized it was a monster fish."

As Oliver passed Adams the line, they soon realized that the creature they had encountered was something more noteworthy than a typical snapping turtle.

The teens used pieces of carp they caught earlier as bait for the fish, which took about fifteen minutes to reel in. Eventually, they saw their catch: the six-foot, 10-inch alligator gar.

An image of an alligator gar swimming underwater. On Sunday, two Texas teens caught a giant alligator gar measuring nearly seven feet in length.Backiris/iStock / Getty Images Plus

"You just have to let it take the bait, but then it's kind of got the same fight as any other fish, except obviously it's just so much bigger than anything else you're used to catching," explained Adams to Chron.com.

After measuring it and posing for some pictures, Oliver and Adams released the alligator gar back into the water.

They believe the fish weighed roughly 140 pounds which, while not a record-breaking weight, is significant for the area: this particular fish is believed to be the largest from the Houston bayou caught in the last ten years.

"People were really freaked out about it, they thought something that big couldn't be swimming in their backyards," said Oliver.

The largest alligator gar on record was caught in 2011, by a commercial fisherman in Mississippi's Lake Chotard. The fish, which was caught by accident, measured 8.5 feet in length and weighed 327 pounds. Astonishingly, the fish was believed to be 94 years old.