Beginner triathlete, nutritional info

Hi there, 

I am just starting swimming, as a way of deciding if i will do a triathlon. I am a runner, but currently injured with a stress fracture which has lead to considering the triathlon. 

I have been swimming for the past couple of weeks with a triathlon club, for an hour 3 times a week in the morning. Doing warm up 6-8 x 4/5 drills to get the front crawl technique then the 6-10 front crawl 

I am really enjoying it, loving a new challenge but as i know nothing about swimming i was just wondering if anyone had any nutritional guidance in terms of swimming? I dont know whether its just me but after the early morning sessions i find im starving even after my breakfast. I also take a  banana before. I find that my heart rate is pretty high during the swimming. 

I would just like to know for future reference, as i only really know about running nutrition

Any help would be greatly appreciated!!