Schengen visa is only for people from certain countries. People from EU (like op) do not need it!
It used to be the case that RCCL required you to have a C1/D so that they could transfer you to a US based ship if they needed to. Now that they have some ships (I think it's 4 at the moment) that never set foot in the US perhaps that's changed? Not having the C1/D will certainly limit the amount of ships that you could go on. Also, haven't you paid out for the C1/D already? I'd be pretty annoyed having paid for something not getting it because they can't be bothered getting you an original LOE.