Not far away in Patong Hospital, a 22-year-old was recovering in Patong Hospital after being rescued.
Lifeguards at Patong were reported to have raced into the water once they became aware that the pair were in trouble.
It's not known at this stage whether the two are athletes from another province, visitng Phuket for the Phuket Games 2012.
Kusoldharm Foundation workers involved in the search said they believed the pair were both from Bangkok.
Most of Phuket's beaches have been popular with youngsters among the thousands who are on Phuket for the 28th National Youth Games, competing in about 40 sports.
The Phuket Games were initially due to be held in January, when the beaches would have been safer. But the big event had to be postponed to May-June because of the floods in and around Bangkok last year.
Phuket Governor Trei Augkaradacha warned officials and coaches earlier in the week to keep their students out of the sea on days when the waves were obviously dangerous.
Lifeguards plucked a child from surf at Kata on Thursday after a group of children from landlocked Sisaket province went into the water.
Locals said the children were inappropriately dressed in long sleeves and pants and the heavy clothing may have meant the boy was unable to stand when hit by waves.
Karon beach, south of Patong, is notoriously dangerous at this time of the year because of monsoon ''rips''.