A former senior manager at Surf Life Saving NSW exploited his position of trust to steal $2.7 million from the charity over 10 years using a complex scam, NSW Police allege.
Matthew Hanks, 50, was arrested in Wollongong on Wednesday and charged with more than 50 fraud offences.
Detectives allege the fraudulent activity spanned from 2006 to 2016.
"It was complex and sustained," Detective Acting Superintendent Richard Puffett told reporters in Sydney.
"These people hold a position of trust and sometimes they exploit that. They are confident, brazen and good at what they do."
SLSNSW reported the matter to police in early 2017 after noticing anomalies in its accounts.
Hanks - who faces a significant jail term if found guilty - had resigned in mid-2016.
He was charged with seven counts of obtaining money by deception and 48 counts of dishonestly obtaining financial advantage by deception.
Det Supt Puffett said the scam against the "iconic organisation" involved the use of fraudulent invoices for vehicle sales and setting up a fake printing company
He said Hanks had spent the funds on his lifestyle and assets.
SLSNSW has launched separate civil proceedings against the former manager and welcomed Wednesday's arrest.
"We have been co-operating with NSW Police for the past three years with their investigations and we now await the outcome of criminal proceedings," president George Shales said in a letter to members.
"We know our members share our anger, disappointment and frustration in this matter and we have endeavoured to keep clubs and other stakeholders informed of progress."
Mr Shales said investigations and reviews resulted in changes to the organisation "to ensure such a situation cannot arise in future".
The improvements were endorsed by the Australian Charities and Not-for-profits Commission, he added.
Surf Life Saving NSW has appointed internal and external auditors, refreshed its finance and compliance committee and overhauled "governance training" for all board members.
Hanks was granted bail and is due to appear in Wollongong Local Court on October 1.
Australian Associated Press