Waterfalls- what to wear?

Hello,

We reserved the 12 Waterfalls option through Iguana Mama and are really excited! I'm not sure what to wear- shorts with a drawstring and a bathing suit top? I'm afraid my swim skirt, which just has an elastic waist, will slide right off. I wore a tshirt in a mud race and it was hanging off of me, so that doesn't seem like a good option. I'm bringing tennis shoes that I can toss afterward. Any advice on what to wear? Thanks!

One piece suit with a change of clothes for the ride back.