The Venturer scouts raised the alarm about 6:00pm when their exit point from the Bradley Chesterman cave became flooded.
The cave is in the same system as the Mystery Creek cave where two school students and a teacher died in 1990.
The Southport fire brigade chief David Cameron said five scouts had to be helped to the surface.
"There was one case of mild hypothermia," Mr Cameron said.
"It was just the requirement of sheer muscle power to help some of these weaker people to get back up this quite steep slope."