The sonar device uses high frequency sound waves and acoustic lenses to find mines and bombs even in dark and murky water.

"Turbid water wouldn't allow video cameras to work," says Ed Belcher who led the team that designed the sonar.

They build each one by hand at a cost of $80,000 each. After they built the first one, these scientists made a startling discovery.

"When we were down at the barge we were running some tests," says Belcher, "and fish would run through the sonar beams, and we were saying 'Look at that!"

Their super-sensitive sonar was seeing salmon. And not just as blips on the screen.

"You can actually see details such as the size of the pectoral fins, tail beats per minute, used to determine species in some cases," said physicist Bill Hanot.

Hanot then developed software that color codes the fish and counts them automatically. Fish and wildlife agencies are hot to use the sonar to help them count fish and monitor migration.

The device has already been used on the Columbia River to see how salmon live near dams, and can be better protected against deadly turbines.