There is a sign when you go into Sea World that says you are not permitted to bring in any food (although they did not check our bags....)
For Lunch, I had the only vegetarian item I could find - a cheese & salad roll. It was premade, so I had to have it as it came. It had Cheese, Tomato, Lettuce, Carrot & Cucumber (which I removed). Quite tasty, but too cheesy for my liking.