It will help if you name at least the cruise and date or the ports of call.......Neil
I visited most of the ports (Vietnam, Borneo, Brunei Singapore etc) about 4 years ago and all visa requirements were sorted out on the ship. Costa should confirm this somewhere in their documentation.
Visas are required for several of the countries for long stays but often being on board ship will avoid you getting one especially for such short periods. So ask your travel agent and if they don’t know get them to find out from Costa because I don’t think you will have to bother but make sure you get an answer from them. I certainly haven’t needed visas in the past with the cruise lines I’ve been with. Regards …Nei.