Time to take a look at that rowing technique of yours! Start by watching this video:

and also check out other parts of Shane Farmer's rowing series in CrossFit Journal:

http://journal.crossfit.com/search.php?IncludeBlogs=1&limit=20&search=shane+farmer&x=0&y=0

Then, practice your rowing technique for 15 minutes. What do you find the most difficult?

By the way, have you ever wondered how the U.S.A. Men's National Rowing Team trains? If you're interested, you might like this Youtube series:

Also, if you want to learn more about rowing, follow https://www.facebook.com/CrossFitRowing to get some good tips and keep your rowing practice going.