Diver snorkeling before struck by boat propeller as seen in Sharm el-Sheikh underwater video of February 13, 2012 propeller strike accident.
Aspects of the Propeller Safety Debate chart
Houseboat Propeller Regulation Proposed and Withdrawn by USCG: Analysis by PGIC
History of Boat Propeller Safety
Mitigating Boat Propeller Injuries & Fatalities Chart