Rafting too, if you don't want to have to put so much muscle behind the oar/paddle.Rowing (w/ 2 oars) and canoeing w/ a paddle both work the heck out of your back and shoulders. Probably the same for rowing machines.If I was buying for a home gym, I'd cop a full cage with a row machine built on, like this: https://www.americanfitness.net/images/products/detail/F430_w_F200.jpgThat way you could adjust the angle from overhead, front, etc. And you can use the cage for other things too.I don't have a cage, so I do dumbbell rows and pull-ups at the park to target my back.