The scuba divers had been unintentionally left behind during an organised tour near Rottnest Island by Perth Diving Academy on March 2 and were rescued by a passing boat operated by Rottnest Fast Ferries.

The men were left around three nautical miles from the WA coast and had been stranded for several hours before being picked up, ABC Perth reported.

They had been taking part in an organised tour by the academy, based at Hillarys Boat Harbour.

The Australian Maritime Safety Authority (AMSA) said it is aware of the incident and is investigating.

“Incidents involving passengers on board Domestic Commercial Vessels (DCVs) must be reported to AMSA,” a spokesperson told 9news.com.au.

“AMSA takes the safety of passengers and crew very seriously and will not hesitate to take swift and strong action should a breach of safety regulations or procedures be identified.”

Both men were left shaken up by the incident and one was later taken to hospital. 

Perth Diving Academy said it was unable to comment as the AMSA is investigating the incident.