A steamboat fitted with an apparatus for removing snags or other obstacles to navigation from river-beds.(noun)
The Century Dictionary (Public Domain)
Use "snag-boat" in a sentence
"About Sioux City, the Government operates a snag-boat, the _Mandan_, at an expense ridiculously disproportionate to its usefulness."
"To be master of the _Atom I_ seemed quite enough; but to be the really truly captain of a big red and white snag-boat -- it must have been overwhelming!"
"And now before us lay the impossible as plainly pointed out, not only by local talent, but by no less a man that the august captain of a government snag-boat."