The trunks are a 4T with a 19.5" waistband. I really love this curved color block view of these shorts. My sewing machine was in the shop, so I left out the buttonhole/drawstring mechanism.
The rash guard is a size 3T with the length of a 4T plus an extra inch (because that was already traced out and seemed like it would work). And because I was working with just the serger and the coverstitch machine, I didn't gather the pocket. Instead I folded the ends in until I had a rough rectangle and then coverstitched it down.
Both fabrics are from The Fabric Fairy. The navy gingham in particular is a gorgeous fabric. It's not slick or shiny and has a spongy, almost cottony feel to it.
I also sewed up a pair of swimsuit bottoms for Z to replace a pair that we lost at the beach last summer. I used the bottoms from the bikini view of the Cosi Swimsuit. They are very high-waisted, so I cut 1.5" off the waist, then serged 3/4" elastic to the top of the waistband, turned and coverstitched. The leg openings were smaller than her legs, so I thought I could leave the elastic out. When I tried it on her without leg elastic, though, the fabric migrated to the middle of her rear, so I put it in. The bottoms look funny because the elastic is longer than the leg opening, but they fit very nicely.
I've got one more pair of swim trunks cut out for Gabriel, and then I need to sew trunks and a rash guard for Niko. It's taking a lot of discipline to stick to my KCW plans, though - I really want to get back to sewing for me!