Start slow and work up to prevent injury.
Sprints will be your friend as far as times are concerned. Run at the pace you would like to run 1/4 mile, then quick walk a 1/4 mile. I usually do 1/4 mile and 1/2 mile sprints at the pace I want to run, followed by a day or two of decent distance (4-5 miles). When sprinting, don't start at a 6 minute mile pace if you are running a 10 min mile. Start higher, then work your way down as you become comfortable. If you are just starting out, keep your distance low. Increase too quickly and you can get injured and it will just set you back (ask me how I know)
50m sprints and 100m sprints are what I do in the pool. Rest the same amount of time your sprints are at. (example, a minute sprint would get a minute rest, you can decrease your rest time as you get more comfortable) Once again, don't do 40-45 second 50m sprints if it takes you 20 minutes to swim a 500. Work your way down. My workouts start with a SLOW 500 to warm up, stretching, sprints, legwork (kicking).
As far as the rest of it, think triathlon, not body builder. Focus on correct form (push ups, pullups, sitsups) and being able to do it over and over again. Believe it or not, doing 100 once is not as hard as it sounds, but can you do it consistently, day after day. Do one heavy day where you use weights, but for the most part, keep things body weight or slightly above (I use a 20lb weight vest for push ups and pull ups), and vary things around the muscle groups. This means don't just do pushups, pullups, and situps, but workouts that focus on the same muscle groups.
Something people forget about it eating correctly and drinking enough water! The majority of what you should be eating is greens (sucks, I know). You want proteins, carbs, healthy fats, and fruits as well, but do some research on how to "feed the machine" correctly for high activity and the amounts you should be having. I also try and get through a gallon of water a day. I don't always do it, but most of the time I do.
Spend lots of time stretching each day and get a foam roller! They are worth their weight in gold.
All this to say, you don't need to spend hours and hours in the gym every week, but you need to focus on the quality of your workout, and consistency. I have an infant daughter and I get my workouts done as I can throughout the day as she sleeps. It's just become my routine.
Good luck!
