If you are really worried buy one of those disposable plastic props
and plenty of extra blades

I've not run aground but I did hit something submerged (didn't notice it until I
tried to reprop) and it broke the anti-ventilation plate.

Because of this, I looked at the plastic/composite props (piranha etc) -- while
the idea is appealing, even the piranha site's reviews made me decide to go with
aluminum over there's for performance reasons.

-j