I love the colours i notes shot Dan, but unfortunately this one isn't quite grabbing me as, for me at least, there isn't a specific focal point i the shot. It must have been great to have watched this, but I don't think the angle you were at has allowed the best shots.
Hi Dan - Always nice to see a water crossing. Unfortunately, I agree with Mike. I think it's that there aren't a lot of heads and eyes visible so that there's a connection with the viewer missing. There's also a purple/magenta cast to the water and bison that I would remove if it were mine. It must have been great to witness but for me it's just not coming through in the image. Sorry.
I imagine this must have been an awesome sighting but I am afraid your image does not quite do justice to the event. Surely the colour casts can be dealt with so I won't dwell on this issue. IMO the problem lies with the framing, the right side of the image leaves me with a strong desire to see more, the "story" you are telling is somewhat incomplete.
Hope you have more images from this sighting, one does not often see this species "in action", it would be good to see.