Dan, the horse's momentum is forward, and the lance doesn't put any force on it, only on the rider. It has to be superglue.
Although, if you've seen "Mulan" you know that it's possible to carry a horse up the side of a mountain while gripping it with you're thighs, so you never know.
I'm not entirely happy with this one. Why would an oil spill bother someone on a water scooter? Those things leave an oily trail wherever they go anyway. The whole concept just doesn't work.