The difference in geometry for air vs. water propellers has a lot of complicated reasons but above all the fluid density of water is about 1000x air: ~1000kg/m3 for water vs ~1kg/m3 for air. Air propellers are optimized for very high-speed operation which is needed to produce any significant thrust in low-density fluid. Boat propellers are very "built up" and physically sturdy since they are used in low-speed operation with high torque.
I have seen people use RC airplane propellers in water for small autonomous boats -- They do work but look very comical (think 10x the size of a boat propeller, running at 1/10 intended speed)
Cavitation effects -- microscopic bursts of vacuum at low-pressure boundaries along the propeller -- come into play much sooner than with air propellers.