If you're walking around Beaver Marsh in the Cuyahoga Valley National Park during the early morning hours, one may spot some talented swimmers along the banks of a river or lake.

These swimmers are known as river otters and they're back home in Beaver Marsh in the Cuyahoga Valley National Park.

The return of the river otters is a sign of the park's environmental health.

"The return of river otters is a symbol of a cleaner Cuyahoga River as these animals prefer unpolluted water with ample fish (and other) prey to eat and to feed their families," said Doug Marcum, a biological technician at the Cuyahoga Valley National Park.

River otters are native to Ohio and were abundant centuries ago, but they started to disappear from Ohio as early as the 1900s due to hunting and habitat changes.

In an effort to get these agile animals back into the wildlife, the Ohio Division of Wildlife started a seven-year project to transfer 123 river otters from Louisiana and Arkansas to their once native home in Ohio. They were first introduced to the Grand River, near the northeastern part of the state and then were released to Killbuck Creek and Little Muskingum River, among others.

Marcum said the otters were first documented in the park in 2013.

"The population has rebounded ever since their reintroduction to Ohio in 1986," Marcum said. "The Cuyahoga River and its associated wetlands offer ample habitat for otters as the population expands."

River otters can be seen throughout the day and night. They are usually 4-feet long with dark brown or gray fur, which often causes people to mistake them for the smaller ancestor, the mink.

Current otter population estimates suggest that river otters may number around 8,000, according to ODNR's Division of Wildlife.

Are you looking to see the otters in action? The Cuyahoga Valley National Park said the best place to spot them is in Beaver Marsh during the early morning hours when the boardwalk is quiet.

When going otter spotting, make sure you are equipped with patience and a camera because they are typically shy and take some time to emerge from the water.