I am reminded of the blade shape of quiet computer fans --- although designed to work in a different fluid, I bet a lot of what applies to making a quiet fan blade also applies to propellers in water.
I don't think air cavitates. There's a fairly gradual transition from incompressible to compressible flow for air, but I don't think that's true for water.
How would air cavitate if it is already a gas?
If you cross the speed of sound with any part of your design or airflow, air can be pretty destructive if your design isn't up to it.
Can’t help but think of computer fans approaching speed of sound! :-)