The men, aged 68 and 61, from the United States drowned when they attempted to cross the reef on their kayaks opposite Koka Lagoon Cruises.
A police spokesperson said they received an emergency phone call shortly before 11am from a Muri Lagoon resort, advising that two of their guests needed rescuing after their kayaks had capsized.
A quick-thinking police officer, probationary constable Junior Tapoki, commandeered a small outboard powered boat belonging to Koka Lagoon Cruises to speed across the 300 metres of water to the edge of the lagoon. However, when he reached them, he discovered the pair had already drowned.
Tapoki recovered the body of one of the men and returned to shore, while police also dispatched the search and rescue Zodiac Lady Kai from Avana wharf, led by Senior Sergeant Epii Poila and probationary constable Osolai Akai, to recover the second victim.
Onshore, police officers and members of the public failed in their attempts to revive the first rescued man after administering CPR for several minutes.
The second victim was taken to an ambulance waiting at the Avana wharf end of the lagoon.
Police have spoken to the daughter of one of the men. She said her father had travelled from the US to Rarotonga to attend a wedding.