The race has been organised by the Bass and Flinders Centre for the last four years to encourage George Town's children to get out on the water.

The event will be held on March 14.

Bass and Flinders Centre managing director Tim Cory said schools were provided with an engineering formula to help in the construction of the rafts.

"Generally they don't sink, occasionally they do though," he said.

"Our biggest problem is once the children are in the water getting them out again. They don't want to come out.

"It starts very orderly to begin with, with children sitting on the boat correctly and paddling away, very soon they are in the water and actually kicking and pushing the boat around."

Mr Cory said it was not too late for people to get involved with the race, which this year extended to Exeter, Scottsdale and Beaconsfield schools.

"We're trying to encourage more people to be involved, because it's a great day," he said.

"It's safe, everybody on the water has to wear a life jacket, and we have about three or four safety boats continually going around."

To get involved, call the Bass and Flinders centre on 6382 3792.