This week I received similar emails from two young men who aspire to become SEALs one day. They both are athletic and involved with sports and asked the following question:
The High School Question
"I'm very uncertain about whether to do winter track or swimming and diving... Have there been BUD/S graduates from USNA who have learned how to swim AFTER they came to the Academy? I'm really not sure what to do and the deadline for sign-up is approaching. Please answer me ASAP! Thanks."
The College Question
"I am trying for an OCS BUDS billet after I graduate college. I am on the swim team now, so swimming is not an issue. However, should I focus more on calisthenics or running before I go to BUDS? Or a mix of both?"
First of all, everybody has their nemesis when they attempt BUDS. Very rarely are there people who are above average in running, swimming and upper body strength / stamina .
Typically, swimmers are not great runners due to years of training in "zero-gravity" conditions. The legs have a hard time taking the abuse of running in boots on asphalt, and shin splints or other overuse injuries tend to occur. 
Runners are typically lighter in weight and upper body muscle strength. They can handle the running at BUDS, but the obstacle courses and daily PT will challenge even the strong.
People who are above average in calisthenics are lean and able to handle multiple repetitions of pullups, pushups, and situps. But they tend to be a bit more muscular and not the best runners. Weightlifters rarely make it. High repetition calisthenics and endurance workouts are much different from power lifting and body building.
My story: I was a typical high school athlete who played sports and lifted weights year round. It took me over a year while at the Naval Academy to change my body from football/power lifter to high repetition calisthenics and muscle endurance athlete. I focused on three things:
Running short distances at fast pace: (3 times a week) This means running for 2-4 miles at a 6-7 minute pace accompanied by a long run of 5-7 miles once a week.
Swimming 1000m-2000m: (3-4 times a week) Technique training with the Combat Swimmer Stroke and one long swim with fins of 1-2 miles.
Upper body and lower body calisthenics: Complete with squats, lunges, pullups, pushups, situps, and other abdominal exercises, I would PT at least 4-5 times a week focusing on upperbody three days and lowerbody on two days of the week.
In closing, you cannot go wrong with whatever you choose for your sport. Do a sport because you like the sport. Squeeze in the missing parts from the above list in your spare time to become better trained for BUDS. Remember have fun while in school! Thanks for emailing me and wanting to become one of the Heroes of Tomorrow.
Have any fitness questions? Send them to me at stew@stewsmith.com. I do my best at answering all your questions or at least directing you to the answers if I do not know them.
EBOOKS
Navy SEAL Workout Phase 1 Beginner Weeks 1-9
Navy SEAL Workout Phase 2 - 3 - Intermediate Weeks 1-12
Navy SEAL Workout Phase 4 Grinder PT - Four weeks before Hell Week
BOOKs
Navy SEAL Weight Training Book
Complete Guide to Navy SEAL Fitness Book/Dvd