I'm not clear what "speak up, not over" means here.

It seems to imply they are alternatives, or have much to do with each other. Speaking up is about refusing to be silent in the face of stuff like racism, and too few of us do that, speaking over is about being discourteous when someone else is speaking and it happens too often in all kinds of contexts.

Rowing? Well there are an awful lot of rowing machines in body building gymnasium settings. It'd make a lot of sense to make it possible for kids who've built up the strength and skills that way to try them out with real boats, and show what they could do.