When there are power boats in operation, there may be a number of causes contributing to propeller strikes on persons:

Incompetence, inexperienced operator, negligence, or failing to follow some basic rules.
Most incidents can be prevented by followings a few simple safety practices.

A person may be injured after falling overboard or while being rescued.

The application of “best practice” SafeBoating and education will assist to reduce incidents.

The benefits of fitting propeller guards, to outboard engines, will also contribute to the reduction of propeller strike injury.

A notice has gone out to all Queensland Scout Formations who have outboard motors, with instructions to cease operations until guards have been fitted.

Scout Groups who are organising water activities with supporting power boats, (private or otherwise), must have propeller guards fitted.

This consideration must also be included in the risk management process.

Refer to Yachting Australia Safety Information notice No. 2 of 2013.

http://www.yachting.org.au/wp-content/uploads/2013/10/sin-2-130826-propeller-guards.pdf