I'm not going (wish I was), but I *think* I'd be okay with it. As long as someone (the ship?) provided fairly nice, inexpensive abayas. I think they are probably fairly cool to wear, although too bad they are not white. Do you really have to cover your face completely with the net thing?
When I was 21, I went to Morocco. Being a young blonde, I decided to try to cover myself, since the men were kind of grabby. So I covered myself with a jellabah, which was really comfortable (it was early spring and coolish). Of course, it is men's garb, not women's, so any foolish idea I had of "passing" was treated with derision.