Biscayne National Park could be the region’s least-known natural treasure.

Encompassing 173,000 acres, most of it underwater, the park is best explored by boat, with fishing and diving as the primary activities. But for residents and visitors who don’t own watercraft, their primary exposure is by touring the indoor exhibits or participating in seasonal family fun fests at the Dante Fascell Visitor Center near Homestead.

But now there’s a free way to tour Biscayne’s unique coastal marine environment: ranger-guided canoe trips into mangrove tunnels like those found deep in the Everglades.

“Gorgeous!” exclaimed Christiana Admiral, the park’s chief of interpretation, after a recent shakedown paddle with longtime park volunteer Terry Helmers and five others.

Weather permitting, paddlers will be guided along a northern route that begins and ends at Black Point Park and Marina or the southern route to and from the visitor center at Convoy Point. The trips take two to three hours and are aimed at all skill levels.

“The park has the largest continuous stretch of mangroves on the east coast of the U.S.,” Admiral said. “We hope to take people who may not have been out on the water in Biscayne National Park to explore a mangrove coastline.”

The trip is a treat for first-timers and seasoned paddlers alike — especially the southern route.

Admiral, Helmers and the rest of the group paddled a little over a half-mile south on Biscayne Bay from the harbor at Convoy Point to the nearly hidden entrance of a mangrove tunnel along the shoreline. Helmers led the way into a narrow creek that — although unnamed — he decided to call Crocodile Creek because it is located within the habitat of the American crocodile, a protected species.

The creek was just wide enough for a single canoe or kayak to pass, and the paddlers had to pull themselves along hand over hand using the red mangrove roots.

The clear waters revealed schools of mangrove snapper and mullet, plus the occasional blue crab. Smaller mangrove crabs climbed the reddish-hued prop roots lining the narrow watercourse.

Helmers noted that the water trees seemed to be unusually litter-free, and he credited volunteers from Vanderbilt University who spent their recent “alternative winter break” performing a heavy-duty shoreline cleanup.

“Beautiful, pristine,” Admiral said.

As the party wound south, the tunnel thinned out and they could see the towers of the nearby Florida Power & Light plant. Soon, they came to a bend in the creek and took the left fork into what Helmers dubbed “Hidden Pond” — an open slough that led to small, scattered stands of mangroves that he named “the mangrove plains.”

Helmers explained that these dwarf mangroves don’t grow as tall as their neighbors because they are anchored in mud flats so shallow that they dry up when the tide falls out.

The group returned through Hidden Pond to the main creek and let the outgoing tide carry them out to the open bay, then paddled north back to Convoy Point.

Helmers, who frequently paddles deep into the remote Everglades back country, said the 2 1/2-mile “Alligator Creek” trip the group had just completed is a good introduction for beginners who might not feel comfortable doing it on their own.

“A person can take this trip and find remoteness and solitude similar to deeper trips in the Everglades, and they’re only moments away from the boat ramp and civilization,” he said.

Admiral said she hoped the trip would show newcomers the importance of the mangrove ecosystem for storm protection, nursery habitat for fish and other marine life, and as a carbon sink that improves air quality.

Added ranger Astrid Rybeck: “We hope this will foster a connection and create an understanding of habitats in their backyard by experiencing them.”