Make a splash in daring colours and prints.Make a splash in daring colours and prints. Junior swimmers will love the sporty style of this vibrant pink Thinstrap Muscleback featuring our iconic Speedo boom design. Ideal for children’s lessons, training and fun sessions in the water, this muscleback style features thin, supportive straps for total flexibility during their swim. Quick-drying and stretchy to keep active kids comfortable, it’s made from Endurance10 fabric which is designed to keep its shape.