I cannot overstate the importance of comfortable shoes! Your feet need to be comfortable all day long. It makes a HUGE difference in your day in the parks!!
I personaly choice is comfortable, broken in sneakers with socks. I also bring an extra pair of socks in case my feet get wet and sometimes just to make my feet feel better. Don’t worry you can buy socks in the stores at the parks as well.
I have seen people wear crocs, flip flops, sandals, water shoes and even heels. Remember you know what is best for your feet. You will be on them for a LONG time so let’s be comfortable.
I know that some people actually carry a second pair of shoes to change into later in the day.