Despite the increasing use of the aquatic environment (AE) as a therapeutic option for activities with infants and toddlers and the increasing number of assessment instruments for land-based physical therapy, no instrument addresses the characteristics of the aquatic environment regarding babies. This study aimed to adapt the aquatic behaviors of the Aquatic Functional Assessment Scale (AFAS) for babies, encompassing infants and toddlers aged three to 24 months (AFAS-Baby). First, a child was observed in the AE by two experts, with adjustments being made by three professionals with experience in the scale. Second, 5 children were evaluated to verify both the scale's applicability and the need for adjustments in it. Lastly, 6 professionals/experts validated the content of the scale. Hence, the AFAS-Baby comprises 61 behaviors: 8 in the Adaptation (A) phase, 14 in Mastering of the water environment (D), 35 in Specialized Therapeutic Exercises (E), and 4 in Global fitness (Cd). The score remained unchanged, following the original scale. The AFAS-Baby enables the assessment of specific aquatic motor behaviors for infants and toddlers, as well as assists professionals in the aquatic stimulation of babies.