Overcome by nerves?

I spent the day at the wonderful Wildfowl and Wetlands Trust centre at Barnes. Sadly the light for most of the morning was poor and flat at best and my photos really didn't do justice to the subjects. However as luck would have it I spotted this little grebe in one of the ponds by the exit as I was leaving. I just had time to snap off a couple of frames before it disappeared very quickly into the reeds - I'm not sure if the white patch behind it was the result of fear, excitement or simply a good meal!