Inspector Les Paterson said that when police got to the scene, one of the teenagers was only partly responsive and appeared to be suffering from hypoxia.
Hypoxia is the result of the body being deprived of adequate oxygen supply and can lead to potentially fatal complications.
A nurse on the beach tried to treat the man but needed specialist equipment.
Mr Paterson said the man was in a serious status two condition, and his friend was described as status three - but police were told an ambulance was not immediately available.
"They were busy with other emergencies. Even though police aren't equipped to properly treat that condition, the officers made the right decision in my books and bundled the two patients into a patrol car and whisked them off to the emergency department,' he said.
"We have previously discussed this sort of scenario with senior St John managers, as emergency services can get overstretched at times, well beyond predicted calls for service. The agreement is the commonsense approach, in that it's a judgment call on the officer's part."
Yesterday St John operations director Michael Brooke said an ambulance was sent straight away when alerted to the swimmers in trouble.
"But en route [they] got a message from the police that all swimmers were ... on shore and safe so [it] was diverted to another higher priority emergency.
"Demand for ambulance services is growing 3.5 per cent per annum. We receive on average 1000 111 calls every day," Mr Brooke said.
"Our focus is to better meet the health needs of our communities by getting to our patients who need us most, faster, and advising people - once we have established through our triaging system it is not an emergency - to look at alternatives."
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