Red-breasted Mergansers

I went back to Burray because yesterday I photographed a shag from distance and only noticed that evening on my computer, that the bird was snagged by a hook and fishing line. It was on a bit of shore that I wouldn't have tried to reach at high tide (nor safe for SSPCA) so I went back this morning. The bird was gone so had 'unhooked' from the rock, but is probably still carrying the material and will get caught again. Alternatively, it broke the line and it fell away. This image shows rbms hustling away from the shore when I appeared. I wonder if the splashing isn't all accidental and is actually a way of confusing a predator like a peregrine trying to pick out an individual bird.