The use of children’s buoyant swimwear has become more common. However, its bulkiness and hardness restrict the wearer’s movement. For better fit, comfort and mobility, a knitted buoyant swimming vest is developed. It is compared with two market samples using subjective evaluation according to the Functional, Expressive and Aesthetic (FEA) Consumer Needs Model and laboratory tests of objective measurements. The results of a paired-sample t-test show that a tightly fitting buoyant swimming vest should be worn out of water, as the vest becomes a perfect fit in water. Tests on the knitted buoyant swimming vest demonstrate improved functionality and higher buoyancy than that of two market samples conforming to British Standard EN13138-1:2014. The results of repeated measures analysis of variance show an overall significant higher satisfaction level in the knitted buoyant swimming vest than two market samples in terms of fit, comfort and mobility. The results of this study are significant for both the textile industry and the fast-growing sportswear industry.