The child has been identified as Mafer Valentina Guevaro of Carlos Street, Williamsville, San Fernando.
Police said the mother, Andrea Medina, was with her daughter around 6 pm visiting her friend Leslie Assam, 25, of B1 East Gate on the Greens, Trincity, where they were bathing in the pool.
On completion, they returned indoors to change when her daughter asked to use the bathroom. Approximately five minutes later, the child did not return nor answered when called.
A search was conducted by her mother and other persons present and she was discovered under the water in the pool.
She was unresponsive when taken out of the water and was taken to Medical Associates where several attempts were made to resuscitate the child but same proved futile and she was pronounced dead at 7:37 pm.
The scene was visited by officers from the Arouca police station and processed by CSI personnel.
Enquiries are continuing.