Definitely not night swimming - the water below didn't look warm or inviting.
It's great to have a walk around town at night with a decent camera. The Gorillapod came in handy too. The chill blowing down the river wasn't so kind, trying to move me on from my spot on the bridge. I stuck it out for a while, but then the wind won and I moved.
I just wish the sky was darker in London. The ambient city light is incredible, and on a cloudy night it is almost like a constant twilight.