I have a idea you might try.. how about having the tRex emit a radial field from the vertices. Have the field pulling in. Although you might run in to the problem of not enough dense geo there.. you could make a high poly dup and hid that in the render. Just a thought. I have not messed with dynamics much but I do know a radial field emitted from the vertex’s of the tRex would be like a static field pulling the water that was close on to it.. might be hard to get the settings right.