the swim could be your undoing if its not your best area. You need to conserve energy for the disciple where you can make up some serious time in the other two disciplines especially in a sprint.
My first sprint I beat my best swim time by a whole minute then lost 3 minutes on the cycle because of slower transition time and cycle due to over doing it on the swim. Its all about maintaining pace and making up time on your best discipline , the bike.
Don't get suckered into trying to keep up with faster competitors . Make sure you keep within your own pace.
Lastly make sure you do at least one full tri in training so you get an idea how much it takes out of you doing three disciplines one after another without a break.
good luck and enjoy it