The tolerances for these modern cruise ships is very high spec. Just because it looks like a container ship with windows doesn't mean it's any less seaworthy. Moreso in fact because the rules for passenger ships is even more rigorous than for container ships. You have to ask the question though, who would want to travel in that? I know the reason they're being built is because cruise holidays are hugely profitable and the demand grows exponentially ever year, but if I was forking out for a cruise holiday I would choose something slightly more elegant to travel in.