SpeedoMen's Swimsuit Jammer Powerflex Eco Solid Adult

How should this suit fit? It's a little snug when I put it on, but it is slightly baggy just above the knees. Not tight at knees like cycling shorts.

“Swimmers: 5X per week 60 minutes per session: how is the swimsuit fabric holding up”

I wear size 31" jeans. What is the best size for me? Small or Medium?

I am a size 29 waist what size should I get