Almost every swim school I know of insist on babies wearing a Splash About Happy Nappy unless they are 100% potty trained, and the one my son goes to is no exception. My son started swimming at 5 months and since then we have gone through the whole range of sizes that the original Happy Nappy comes in.
I was really looking forward to trying out the new Splash Jammers that Splash About has brought out specially for toddlers that were potty training. It comes in two sizes, age 2-3 and 3-4, and also in a pink flower print version for girls and the shark print for boys. Like the original Happy Nappy, Splash Jammers provide all the assurance of a Happy Nappy but in a more grown up and sporty design. Splash Jammers are designed to minimize the risk of feacal leaks, with an ergonomic form fitting shape, specialist fabric at the waist and medical grade silicone on the thigh, and can be worn alone or as part of the double nappy system, as required by your swim school.
The difference between Jammers and the original Happy Nappy is generally the look and fit of it. The Jammers feels thicker compared to the Happy Nappy. The Jammers also looks better at the tights as it has lost the gusset and in its place has the silicon seal which is not visible. I definitely prefer the look and feel of the Jammers and it does have a big boy look and fit compared to the more babyish Happy Nappy. It gives a potty training toddler more confidence as the Jammers look different from the Happy Nappys but still give them the protection in case of little accidents.