According to the company that sells swimwear on our swim team, you need to measure the boy's waist to determine the size of the swimsuit to order.
I think we ordered 28 for my six year old who is a little heavy (husky clothes are too big but regular clothes are a little tight). It has a durable feel and the bright color makes it easy to find in a bag.
LUCOWEE Anti Chafe Boys Swim Trunks: Boxer Brief Liner & UPF Quick Dry Technology
55 Review
π©² Boys' Protective Swimming Bottoms by City Threads - Swimwear for Enhanced Safety
56 Review
Platinum Rashguard for Boys by Kanu Surf
54 Review
π Stay Safe in Style: Kanu Surf Boys' Protective Rashguard in Charcoal
44 Review
π Bold Pack Sleeve Active Hoodie Sweatshirt Set for Boys' Clothing - Stylish and Comfortable!
47 Review
Arctix Youth Pants Reinforced: Large Boys' Clothing for Active Adventures
46 Review
π₯ Stay Warm and Active with Rocky Fleece Thermal Underwear Bottoms for Boys
44 Review
Boys' Adidas Active Sports Tricot Athletic Clothing
45 Review