Notes from the artist:

The building at the St Katherine Docks in which I had my studio was surrounded by water. In order to go to my studio I had to cross a small wooden bridge, and it was from this bridge that I noticed things floating on the water; and every day I found them at different places. It was their movement from one place to another that began to fascinate me; and I would often stop at the bridge to watch them. And, eventually, this fascination for the movement of the things floating on water became so obsessive that I decided to intervene.  So, at the end of 1969 I decided to make 16 circular wooden discs, 24-inch diameter each, and painted red, so as to float them on the water along with what was already floating there.  In February 1970, I asked some people from the studio to participate in the act of throwing these discs on to the water; which we did collectively. I followed the discs with a camera and documented their movement; every day for two weeks.  Some of them eventually left the water of the docks and floated away into the Thames.