"We got the call from the police and were on our way but Phoenix was right there and acted quickly. It was lucky they stayed calm and stayed on their boards because swimmers can panic when they get caught in a rip and pull a rescuer under."
Newell said he also credited the member of the public who called the police when they noticed the boarders were in trouble.
Whanganui surf lifeguard patrols begin at Castlecliff and Kai Iwi beaches on Saturday and will continue every day from midday to 6pm until January 30.
"Lifeguards will be on duty on Christmas Day and New Year's Day and we ask that beach visitors help them out by swimming between the flags and observing good water safety practices," Newell said.
It was timely to remind swimmers to watch out for rip currents, he said.
"If caught in a rip current, relax and float, raise your hand to signal for help, ride the rip until it stops and you can swim safely back to shore."
"If in doubt stay out and ask a lifeguard for advice as conditions can change regularly."
Newell said it was important to always keep a very close eye on young children in or near the water and keep them within arm's reach at all times.