I won't pretend to know the ins-and-outs of dragon boat racing, but I will make educated guesses based on the movement, the body language, and the faces of these people, educated guesses as to what is going on.
These two teams appear to be taking advantage of one of their last chances for a hard practice before the actual races on Saturday. They are hot at it.
Once the boats got close to the west bank of the river, they eased around and headed back out into the river.
It appeared the people on this boat were practicing their response to some cue from one of the non-rowers on the boat. They held their paddles up at a certain angle, then dug deeply into the water, over and over and over.
Then they headed back out onto the river proper for more practice.
Depending on the weather, my chores at the apartment and timing of life in general, I plan to attend Saturday's races, and take more photos, of course!
By the way, about these photos, I don't have any photo-altering software other than iPhoto's enhance and/or lighten and darken slider thingeys, so please don't think I'm talented enough to outline those flowing-dragon-parts to make them stand out in front of the river. It's serendipity brought on by the angle, I suppose.