Aqua Balloon 12cm. The Aqua Balloon has outstanding clarity, resilience, and expandability, and becomes an almost perfect sphere when inflated. The film surface retains transparency with hardly any clouding, it is extremely soft and pleasant to touch, and has excellent air and helium retention even when tied by hand. You can inflate a 12.5 cm Aqua Balloon from a minimum of 13cm to a maximum diameter of 23cm (10 inches).