Hi Julie,
I eat breakfast, wait at least an hour and then go swimming. If it feels like it's still sitting in my stomach, I wait longer. My body is so happy eating a complete breakfast and it helps me have the energy to exercise. I have a small snack afterwards.
If you can manage it, another idea is to wake up a little earlier and eat your whole breakfast right away, so you have time to digest it. There's a separate list for this topic so you might find more in depth that way. I'll be joining you there at some point once I ramp up my routine.