OFF THE KEWEENAW PENINSULA, MICH - It was a perfect day for shipwreck hunting.
Lake Superior was placid, and summer sunshine warmed Kraig Smith's tanned, stubbled face as he pitched the torpedo-shaped "tow-fish" over the side of his 22-foot C-Dory and watched the cord play out into the wake.
Smith's friend Jerry Eliason was at the helm of the boat. He kept a precise course with a GPS unit, while monitoring a laptop screen receiving signals from the tow-fish -- a pet name for their homemade sidescan sonar transducer.
Somewhere down below, hidden in 500 feet of water, lay the wreckage of the Sunbeam, a wooden sidewheeler that sank with at least 25 passengers in 1863.
Eliason, Smith and two friends are determined to find it. They are a rare breed.
They are adventurers who spend much of their spare time and money searching for the shipwrecks that litter the bottom of Lake Superior.
"There are only about 50 serious wreck hunters on the whole Great Lakes, and those guys on western Lake Superior are in the top five," said Brendon Baillod, a maritime historian who runs www. ship-wrecks.net, a Great Lakes shipwreck research website.
About 100 Lake Superior shipwrecks remain unaccounted for, while the locations of more than 200 other submerged wrecks are known.