Swim Trunks. I bought medium for my 4 year old and large for my 7 year old. Both fit well - the medium was a little loose on my 4 year old but didn't fall off when tied. The big one was tighter on my 7 year old but not too much. Fits well. We're still using them a year later and they're in great condition! My youngest son likes them better than swimming trunks!
Waterproof Cozy-Dry Rain/Snow Pants for π§ Kids by JAN & JUL, with Fleece Lining
64 Review
π Boys' Outdoor Climbing Convertible Trousers - Waterproof | Clothing
47 Review
π Fruit of the Loom 6 Pair Cushion Ankle Boys' Clothing: Comfy and Stylish Selection for Active Boys
57 Review
Boys' Adidas Active Sports Tricot Athletic Clothing
45 Review