BORDER TEAM -- The locals consider it a secret gap in border security: a sand trail in the gulf that you can only see during low tide.

It links the U.S. and Mexico at the mouth of the Rio Grande River. Fishermen, there said one can simply walk back and forth between the two countries without being caught by authorities.

At the south end of Boca Chica beach, where the gulf water meets the Rio Grande River, there’s a corner of the border where fishermen like to gather.

On fisherman, 32-year-old Rene knows the area well. He has fished here since he was 8-years-old and said he goes there almost every day.

“That’s what I like to do,” he said.

He said it’s a popular spot for both Mexican and American fishermen because fish collect in a basin, which is surrounded by a sand barrier between the sea and the mouth of the river.

Here, the border lines are blurred.

Rene points to the strip of sand populated by birds and pelicans. He said one can simply walk across, especially during low tide. To those who frequent this area, it seems obvious.

“It looks like an easy spot,” said winter Texan Juan Olivo.

Olivo said this area gets crowded on weekends, especially on the Mexican side. Although he and his wife come here to leave their worries behind, they like to keep a watchful eye on things.

“People can do a lot of stuff through here,” he said. “[They] come out here and go around and do that.”

Both Juan and Rene said it’s safe in Boca Chica. Authorities are often seen patrolling the area.

“Even at night, they do it. They patrol it 24/7,” Rene said.

And so, KENS 5 Broder Team decided to put that to the test.

The Border Team returned a week later. Up the only paved road out of Boca Chica, is a Border Patrol checkpoint. Two agents man the post even as early and as late as 4 a.m.

But back at the beach that morning the only people in Boca Chica are Mexican fishermen. The Border Team even caught some on a boat net fishing in U.S. waters.

As they stand on the sand bar, the fishermen claimed to be fishing on the Mexican side, but admit that the low tide can allow them sometimes to walk to the U.S.

The sand bar is not always obvious to the naked eye, and depending on water levels, one must swim to get back.

It took the KENS 5 Border Team less than five minutes to make it back across. There were no signs of law enforcement, no one to keep them from making it to the American side.

Here, there is no border fence, just a narrow stretch of river and then, a sand trail. It’s a little-known secret told only at Mother Nature’s discretion.

In a statement, Border Patrol assures that there are other measures in place, including sensors, and cameras in addition to the patrols to keep this corner of the border secure.