The OP from Navy18 is spot on. I have a plebe son at USNA this year and his story is quite similar to Navy18's. Plebe Summer, while difficult at times, was a walk in the park compared to the AC year, so far. And, in terms of status at the Academy, even the highest achievers in academics, sports, leadership, etc are really just 'normal.' It truly doesn't matter your background, you will most likely be "average" at USNA if you are fortunate enough to attend. There are so many impressive kids at the Academy it often makes our heads spin!
For some background, our son graduated in the top 1% of his class (5/500), was a State Scholar (1,300 Valedictorians in our state vs. 147 State Scholars), was a 3-sport varsity athlete (football, basketball, track), team captain in each, student government all 4 years, president of the largest club at school (100+ members), and had loads of academic awards (state, national, international) and other impressive EC's, which even included working as a paid engineering intern for 2 months with a NASA astronaut. He is "average" at the Academy.
Our son received his LOA in November of 2013 but waited to commit until late April 2014. He attacked Plebe Summer with enthusiasm and made it through with a few bad days, but mostly good ones. Then the AC year began. I think he would tell prospective candidates that the AC year is probably 50% more challenging than Plebe Summer. Time management is definitely the key to success! Sleep is a precious commodity and tough to fit in during the weekdays -- plan on 4-5 hours a night with an occasional 6 hour "sleep in" here and there.
Similar to the OP, our son has been rowing varsity [plebe] crew from the beginning. Doing a varsity sport eats up 2.5-4 hours every day, which is why many varsity athletes often fall behind in academics - which happened to our son. Where "A's" were always automatic in high school, they are much more difficult to obtain at USNA. I believe the "average" GPA for plebes (almost all of whom were academic stars in high school) is somewhere around a 2.8, with approximately 25% of the class being UNSAT at any given time (i.e. two D's, or under a 2.0 GPA). Additionally, with the stress of all the other military duties, company requirements, mandatory briefings, etc it is difficult for your body to stay healthy -- especially without adequate sleep. Many kids are sick for weeks and weeks. Unfortunately, this happened to our son at the beginning of both 1st semester and 2nd semester. He ended up with Mono after battling illness for 6 weeks at the beginning of the school year and recently just finished a round of antibiotics after being sick another 4 weeks at the start of the 2nd semester. Not quite the same experience he would likely be having if he were at a state university like many of his friends.
No doubt that academy life is challenging. But, as our son has attested many times, "I am 100% positive that I belong here and while I hate it some days, I am in love with it always." USNA is the best place in the world for building character and leadership and the future could not be more bright for those who attend.