I knew that our own government agents, as well as foreign ones, were keeping keen watch over all the roads and rivers, all the lakes and the coasts of America.

Throughout rapid developments in undersea cable networks, global satellite systems and burgeoning digital technologies, OTC maintained a keen watch over its services to ensure continued quality.

As she swam, she kept a keen watch for threats from the many dangers in Zazesspur's coastal waters.

Indeed, his men kept a keen watch once we'd rounded the point, sharpening their swords and manning the trebuchet mounted atop the forecastle, but we passed unmolested.

Shrouded in darkness, The Shadow kept keen watch.

His unaided eyes were as good as the ordinary man's telescope, and he kept a keen watch on the fringes of the great birch woods.

They keep a keen watch on their forest.

Mr. Sulu, Mr. Chekov, keep a keen watch.

Mike went on guard in the morning and kept a keen watch.

They gathered behind the center field fence, where they kept keen watch on the calls of the home plate umpire.