Lean Swimmers: What do you Eat on Race Day?

Since I have low body fat for a woman and am not naturally buoyant, I can't eat much on race day or it sinks my body position enough to hurt my swims. Some of my best swims have happened on days where my stomach's been upset and my GI tract fairly empty. Lately, the sugary gels, sports drinks and smoothies I've consumed in the past are making me shaky. I'd love to hear some nutritional suggestions for race day. Thank you in advance for sharing your thoughts. :)