Rowing is the sport or activity of making a boat move through water with oars. As a hobby it can mean a quiet afternoon on a lake. As a sport it is hard work: long boats, timed strokes, races. The word is just row plus -ing. Though actually English has a trap here. This row sounds like “go.” There is another row that means a noisy argument, and that one sounds like “cow.” So “rowing” the sport and “they were rowing” meaning “they were fighting” look the same on the page and are not the same word. In American English the argument meaning is less common, so the trap is smaller, but exam English still uses both.