Nutrition
Healthy food and nutrition is the fuel that an athlete’s body requires to grow and strengthen.
Your body's muscles break down after a workout, and uses proper nutrition to repair and grow stronger. Swimming can burn up to 800 calories per hour, in addition to a normal 2000 calorie diet. While it is important to eat healthy, it is more important for growing athletes to simply eat enough.
Food should be consumed more than an hour before a workout or competetion. Some athletes do not need to eat before a 6am morning practice, but it is absolutely required to eat breakfast after practice as well as during lunch. Proper nutrition is especially important the day of and day before a competition.
Examples:
Before practice - fruit, granola bar, toast, bagel
After practice - Carbs and proteins, ideally within 30 minutes after pracice
During the day:
Carbohydrates - pasta, rice, whole grains, bread, potatoes
Protein - chicken, fish, lean meats, beans, eggs, milk, nuts and legumes
Vegetables and Fruits - several servings a day
Water - constant hydration throughout the day
Foods to avoid - soda, chips, junk food, deep fried foods, excessive fast food, sweets and desserts
A good article with more detailed information can be found here:
https://www.swimmingworldmagazine.com/news/the-big-deal-about-a-swimmers-nutrition/