THE Caloundra Coast Guard members know the bar like the backs of their hands.

But even they admit it's unpredictable - and the main cause of need for the Coast Guard's assistance.

The Coast Guard keeps the waterway safe, from halfway down to Bribie Island all the way up to Point Cartwright.

Volunteer John Gasparotto said the group's four crews could assist with anything from a boat fire to breakdowns to overturned tinnies.

The bar, the gatekeeper to the open water, is what causes most concern.

"The bar always changes," John said.

"You head out there and you could go one way but then you find you run out of water."

He said the Coast Guard was pushing for people to log in by radio and report their intended activities.

"Log in and say, 'We're going to go fishing off the Blue Hole. We expect to be back by 3pm'," he said.

"It's simple, and if by 3pm you haven't signed off, well, then we know there is a boat missing and we'll go looking."

Commander Tony Barker said the more people logged in, the safer the water would be.

"We've had a few instances where people call up and say they had a family member go out and they hadn't come home yet," Tony said.

"If they log in with us and give us an estimate on when they'll return, we can go and look."

With about 95 assists a year, John said they were always looking out for more volunteers.

"We currently have 82 volunteers, which includes boat crew, base radio operators and fundraisers," he said.

He said each weekend they were out on the water training to enhance their safety skills.

Skipper Harley Moss said the boat they used for patrols was unique.

"You can move out parallel and go into really shallow waters," Harley said.

With a GPS, defibrillator, oxygen, spinal board stretcher and electronics constantly changing to keep them up to speed, the purpose of the design was to be a search and rescue vessel.

He said they spoke to boaties on the water and offered advice.

"On the Easter weekend, we saw a man with his three young kids about to cross the bar but we advised him not to," Harley said.

"The ocean is absolutely gorgeous, but it can turn from a beautiful sunny day into a nightmare."