Swimming is a great exercise!
The healthiest foods are whole foods (unprocessed)
Chicken (Unless you're not a meat eater)
Seafood ( " )
Potatoes especially sweet potatoes
Beans (pinto, lentils, navy, green beans, etc..)
Fruits especially berries
Google "Quick Easy healthy meals" that should give you tons of recipes, to teach yourself how to cook. There's nothing like eating your own cooking
Oh and don't forget spices. Spices are good for the body!