"One in five passengers confessed to cheating on their partner on a cruise ship"
This conclusion was jumped to from "insights" published by www.cruise.co.uk who polled their "200,000 strong cruise community" (no mention of how many responded) and found that 17% said "Yes" when asked "Have you ever had sex with someone on a cruise other than your husband, wife or parter (sic)?"
News Flash: Single people have sex on holiday too. Having sex with someone other than your husband, wife or partner does not make you a cheater if you don't have a husband, wife or partner. Also, having sex with someone other than your husband, wife or partner does not make you a cheater if you were not with your current husband, wife or partner at the time.