Boys swimming shorts with yellow and white stripes, fully lined with an elasticated drawstring waist. Matching girls swimsuits with the same pattern also available. Also available in mint green, pink and blue.
 
These do come up a little small. Measurements of the actual swim shorts:
2 Years: across the waist 23cm, length 28cm
4 Years: across the waist 25cm, length 30cm
6 Years: across the waist 27cm, length 32cm
8 Years: across the waist 29cm, length 34cm