Bull boats were the coracles of the American Indians of the Great Plains, including the Lakota, Mandan and other Sioux, Cherokee, Assiniboine, Blackfoot, and others. Typically round and 8' or 9' in diameter, they were strictly women's craft among most of these people. Like the coracle, they were paddled by sitting (or standing, according to one account!) in the "bow" (i.e.,near the edge of whatever direction you were facing), placing the paddle in the water directly in front of you, and drawing the paddle toward you. Although there are some historical references to how fast they could be paddled, these must have been charitable or ignorant statements, for a boat like these could not possibly go fast by any objective measure, and from a design standpoint they really are about the slowest boats possible.
Named for their bison-hide covering, bull boats did not have the neat and elaborate framework of the coracle of the British isles. Rather, their frames were built with flexible sticks of varying shapes (often willow), and not all of them by any means straight. Not intended for long-time use, but intended to be portaged by women daily, they were lightly built, with "frame spacing" very large -- from photos I've seen, spaces between frames may have been nearly a foot in some instances.
Oddly, the hair was left on the hide, and the hide was attached with the hair side outward. This would have made a slow boat even slower (and heavier, when wet), but the hair probably fell off or wore off before long. The boats were removed from the water daily to dry, as they would have quickly rotted otherwise.
Most had an uppermost "gunwale" (at the top ends of the cross-frames) over which the covering was stretched, but in some (as in the illustration above), the cross-frames extended above the uppermost circumferential frame and the cover was attached to the ends of the cross-frames, giving these models somewhat of an inverted-umbrella look. Some Mandan people apparently used this method. Another charming feature is that the tail of the bison was left on, serving as a painter.
As women's craft, they were used for chores -- hauling firewood and such. With bison hide such a readily available staple of the Plains Indian economy, and with their simple frameworks, they were not considered highly valuable -- more "disposable," in fact -- and were probably abandoned readily and replaced with a new one when needed.
The 1833 illustration by Karl Bodmer shows Mandan bull boats.