Check out the legs on this guy! Bear in mind that he is over 2 metres tall (6" 7) and, when he was competing, he weighed over a 100 kilos, so he is hardly what you would call of a stocky build.
The holy grail of the rowing world is the single scull: it is just you and your boat, noone else in the crew, not even a cox to steer you (you have to steer with your foot which is connected to the rudder, looking over your shoulder from time to time). Even the mighty Steve Redgrave "only" managed to get a gold in the single scull in the Commonwealth Games. (What a wonderfully British euphemism the word "Commonwealth" is.). As you are moving much more slowly than a rowing 8, your oars spend more time in the water and technique is much more of a factor: how quickly you "catch" the water, how smoothly you accelerate without ripping through the water, how good your rhythm is, how explosively you coordinate all the muscle groups (we're going to assume that balancing the boat is not an issue!).
So how come you haven't heard of arguably the most successful single sculler of all time? He won three Olympic gold medals at three consecutive Olympics, a feat only equalled by Vyacheslav Nikolayevich Ivanov. Maybe its due to the fact that it is impossible to remember where to put the double letters in his name (unless you are Finnish, of course) which makes it is harder to find him on the internet. I read that at the age of 52 he was able to row 2000 metres on the Concept II Rowing ergometer (typically found in most gyms) in 5 minutes and 52 seconds - that means pulling at a 500m split of 1:28 for 6 minutes! Try it sometime.