Most cruise ships don't have specific man-overboard sensors. However, they are becoming more common with advancements in fall detection technology and cruise lines continuing to improve the safety and security of guests and crew. Ships that don't have overboard systems must rely on other passengers or crew to see the person fall overboard and alert the staff. If a person falls overboard without anyone seeing them, it may be hours or days before anyone notices that the passenger is missing. At this point, the cruise ship may not be able to identify when the incident occurred or how it happened. There are CCTV cameras throughout the cruise ship. However, the cruise ship doesn't continuously monitor the security cameras. Typically, the cruise line and investigators use CCTV footage after the fact as evidence in determining the cause of the fall.