Med islands/bike hire
Here you go, from my earlier web link:-
Shipping to Corsica Sardinia - shipping company Corsica Ferries
Not clear to me why you want to take a ferry there if you are not taking a bike - have you thought about a cheap flight into the island and then hiring whatever.
My memory of Corsica (unfortunately not there with a bike) is of the "rugged routes" in and over the mountains, where many of the local riders do not bother to wear helmets and are not too bothered about such things as rules of the road - From my various visits to islands of the med, this is not unique to Corsica!
I have hired wheels in Ibiza - as Steve says, the locals tend to be one-man businesses, so you will have to look for them (but the internet will help a lot in that regard). I just hired "on spec" while on the island.
I also saw some info a short while ago about one of the major car hire companies starting to offer bike hire; I think it was Hertz (and that may have been in Canada only!??)
Anyway, enjoy, whatever you decide to do,