(CNN) -- The first clue was a boat floating in the ocean with no one on board.
So teams of rescuers took off, unsure of they were looking for when one crew saw the unmistakeable second clue.
There on a sandbar were three huge letters -- S.O.S.
And there on a nearby rocky island were five people on a rocky outcrop off the northeastern coast of Australia, happy to see a helicopter after eight hours of waiting.
The incident occurred Monday when five people were snorkeling in the Pacific Ocean. They anchored their boat near the sandbar, the Courier-Mail newspaper of Brisbane reported, but the boat drifted away after its anchor broke.
They stamped out a large distress signal in the sand, but they knew it was only a matter of time before the tide claimed the signal.
The rocks were high enough, but the group had no phones or food, which floated away with the boat.
"We were a bit (sun)burned and it would have been fairly cold (if they had to stay out through the night)," Lyn Forbes-Smith told The Courier-Mail. She said they had gone diving at 8 a.m. and were picked up about 4 p.m.
A helicopter rescue crew from Central Queensland took off and after an hour spotted the SOS.
"We did two sweeps and then when we came across some guys on the rocks and we saw SOS written in the sand so we knew it was them straight away," crew member Damien Kross told Seven Network. "It was actually quite good because we knew we found them."
By the time the helicopter got there, the water level had made it impossible to send a boat in for a rescue attempt.
The crew used a winch and basket to bring the three men and two women into the helicopter. Kross said the five were in good spirits despite being a little dehydrated.