The first stage is to race across the ice of the starting harbor, before getting out into the open river.Yes, they are pushing across the ice as it cracks underneath them.The second stage, after the harbor, is to paddle upstream into the oncoming bergs. They do this on side of the river with less ice, so they can get as far upstream as possible before stage 3.
Stage 3 is when they cross the solid ice floe. This youtube video gives you a sense of how intense this is.
Finally, they tag the post on the far shore, and complete stages 4-6: going back the way they came.
Here’s what the river looks like on a nice, sunny day:
Tea and Kate 