Im 17 and trying to loose weight help?

im a 17 year old male i weigh 205 a little overweight you can say. im trying to get down to 170 by school please give me some tips in the morning i go swimming before i eat so i burn more calories i swim and do laps for about an hour im trying to eat healthy vegie burgers tuna eggs fish chicken exc... how long till i notice results and is my goal even possible also ive benn told if i swim in the monrnig intense laps with an empty stomach i can burn up to 1000 calories is that true and im trying to consume less than 2000 calories a day thanks for the help