Set it up about half out of the water if you can ,depends on the angle of approach . You can funnel with brush or dead sticks and try a chunk of fresh poplar right behind the trap . good luck
Steve, by the sounds of it, you are not a trapper. If this is on your own private land, I would suggest you acquire the services of a trapper, or have one show you how to trap them.
Here is a link from the agriculture dept that has some good info for managing them. For my pasture, I don't mind them damming the creek as they thin out the poplar along the banks and maintain a water level for the spruce to then thrive. If they move into the natural spring runoff areas I get them with a 330 conibear and then install a chunk of that black corrugated 6" pipe to keep others from rebuilding the dam.
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3469