Thank you everyone for all your replies. I guess there is no clear rule in this case. What I did last weekend, seeing 4 rowing crews abreast, was to steer clearly around them letting them keep their formation. I don't think it was a race, but I could not be sure. They seem to be out every Sat and Sun morning practicing. And they are in a narrow channel that we use to go from harbor out to the lake. So yes, inland water rules would apply.
I can keep steering around as long as I am not too close to the shallow areas near the shore; we draw about 4 feet.