I thought this was a huge moth in the water (as big as my hand). It would rest for a bit and then madly paddle. It was right in the middle. I hope it was a moth - its not a bat is it?
Whew. Thanks Harvey. Though I still feel bad for the moth. It was doing a good job of motoring across the water though kept to the centre where there was less likehood of finding one of the many twigs to get up and out on.