The "medical experts" and "researchers" say that SPF 30 is the stongest sunblock there is in terms of SPF here in the US. Anything higher is not really "better". It is just a way to get people to buy it. However the news here in the US lately is that there is a better sunscreen used in Europe, but the FDA here has not approved it for us yet.
As for the tanning beds, common sense will tell you "everything in moderation". My opinion is a month of tanning before a cruise, no greater than every year, is probably better than burning on the cruise. If you don't plan on getting in the
much on your cruise, then sunscreen applied appropriately is probably enough. I just know that when I went on a cruise, I wanted to lay by the pool, snorkel, lay on the beach, and many other outdoor activities. Being somewhat fair-skinned and strawberry blonde, I knew I would burn if I didn't have a base tan and even if I used sunscreen. I still use sunscreen to protect from burning and the other harmful damages associated with sun exposure. But I know everyone is allowed their own opinion! 
As for the tanning beds, common sense will tell you "everything in moderation". My opinion is a month of tanning before a cruise, no greater than every year, is probably better than burning on the cruise. If you don't plan on getting in the
much on your cruise, then sunscreen applied appropriately is probably enough. I just know that when I went on a cruise, I wanted to lay by the pool, snorkel, lay on the beach, and many other outdoor activities. Being somewhat fair-skinned and strawberry blonde, I knew I would burn if I didn't have a base tan and even if I used sunscreen. I still use sunscreen to protect from burning and the other harmful damages associated with sun exposure. But I know everyone is allowed their own opinion! 
