The dive instructor who left his lookout to go to the bathroom when skipper Leila Trott disappeared on the Great Barrier Reef says her death was a "freak occurrence".
Ms Trott, 38, is believed to have died from a sudden cardiac episode while swimming to retrieve a dinghy off Green Island on April 6, 2016.
Filippo Matucci told the inquest into her death on Thursday he stopped watching Ms Trott swim so he could go to the toilet for two minutes, but what happened to her was a freak occurrence.
AAP