The simple answer is AT LEAST 16. However, there is a little more to it and maturity plays a big factor. Expert opinions on the topic varies and some believe the age should be as old as 18. There are other training agencies that will certify lifeguards at 15. The Unites States Lifeguard Standards Coalition’s published 2011 report only gives minimal guidance on the subject. The guidelines suggest “lower-stress and lower-risk” lifeguard jobs can be filled by 15 year olds, “higher-stress” lifeguard jobs should be performed by someone at least 16 years old.
The guidelines only give vague suggestions on what low-stress and high-stress lifeguard jobs would be. As a training agency that does not know what kind of lifeguard job its students will be filling (low vs high stress), we put the minimum age of being certified at 16. We have also given instructors the ability to withhold certification from anyone the instructor believes lacks the maturity to be a lifeguard. Although somewhat subjective, maturity matters and we only want to certify people that can perform lifeguard duties in a manner that protects patrons.