pls select the size by referring to the foot length or the inner sole length.

Size Info:
US 5.5 Toddler=Size 21=inner sole length 5.31in= foot length 5.12in
US 6 Toddler=Size 22=inner sole length 5.51in= foot length 5.31in
US 6.5 Toddler=Size 23=inner sole length 5.79in= foot length 5.59in
US 7 Toddler=Size 24=inner sole length 6.02in= foot length 5.83in
US 7.5 Toddler=Size 25=inner sole length 6.29in= foot length 6.1in
US 8.5 Toddler=Size 26=inner sole length 6.57in= foot length 6.38in
US 9.5 Toddler=Size 27=inner sole length 6.77in= foot length 6.57in
US 10 Toddler=Size 28=inner sole length 7.09in = foot length 6.89in
US 11 Little Kid=Size 29=inner sole length 7.36in= foot length 7.17in
US 11.5 Little Kid=Size 30=inner sole length 7.6in= foot length 7.4in
US 12.5 Little Kid=Size 31=inner sole length 7.87in= foot length 7.68in

Toddler Boys Girls Water Shoes Quick Dry Beach Sport Swim Slip on Sandals Little Kid