Check out the Columbus crime rate for 2004:
<TABLE cellSpacing=1 cellPadding=4 width="100%" border=0><TBODY><TR bgColor=#e5edff><TD>
Crime Type</TD><TD align=right></TD><TD align=right>
2004 Total</TD><TD align=right>
Per 100,000 People</TD><TD align=right>
National per 100,000 People</TD></TR><TR bgColor=#e5edff><TD>
Overall Columbus Crime Index</TD><TD align=middle>

</TD><TD align=right>62861</TD><TD align=right>8612.2</TD><TD align=right>3982.6</TD></TR><TR bgColor=#ffffff><TD colSpan=5></TD></TR><TR bgColor=#e5edff><TD>
Columbus Violent Crimes</TD><TD align=middle>

</TD><TD align=right>5925</TD><TD align=right>811.7</TD><TD align=right>465.5</TD></TR><TR bgColor=#e5edff><TD>Columbus Murders</TD><TD align=middle>

</TD><TD align=right>88</TD><TD align=right>12.1</TD><TD align=right>5.5</TD></TR><TR bgColor=#e5edff><TD>Columbus Rapes</TD><TD align=middle>

</TD><TD align=right>574</TD><TD align=right>78.6</TD><TD align=right>32.2</TD></TR><TR bgColor=#e5edff><TD>Columbus Robberies</TD><TD align=middle>

</TD><TD align=right>3353</TD><TD align=right>459.4</TD><TD align=right>136.7</TD></TR><TR bgColor=#e5edff><TD>Columbus Aggravated Assaults</TD><TD align=middle>

</TD><TD align=right>1910</TD><TD align=right>261.7</TD><TD align=right>291.1</TD></TR><TR bgColor=#ffffff><TD colSpan=5></TD></TR><TR bgColor=#e5edff><TD>
Columbus Property Crimes</TD><TD align=middle>

</TD><TD align=right>56936</TD><TD align=right>7800.4</TD><TD align=right>3517.1</TD></TR><TR bgColor=#e5edff><TD>Columbus Burglaries</TD><TD align=middle>

</TD><TD align=right>14695</TD><TD align=right>2013.3</TD><TD align=right>729.9</TD></TR><TR bgColor=#e5edff><TD>Columbus Larceny/Thefts</TD><TD align=middle>

</TD><TD align=right>33844</TD><TD align=right>4636.7</TD><TD align=right>2365.9</TD></TR><TR bgColor=#e5edff><TD>Columbus Motor Vehicle Thefts</TD><TD align=middle>

</TD><TD align=right>8397</TD><TD align=right>1150.4</TD><TD align=right>421.3</TD></TR><TR bgColor=#ffffff><TD colSpan=5>
http://columbusoh.areaconnect.com/crime1.htm
</TD></TR></TBODY></TABLE>
The cruise ships don't do background checks on passengers for a criminal record and I doubt that they do much of a background check on their employees either. With 3000 to 4000 people an average ship in a relatively small area (and especially with most of the passengers drinking more than they are accustomed to) an occasional crime on a ship is probably inevitable. Their biggest problem (and the major complaint) is that when a crime does occur they do not do a good job of investigating it. Also, nobody is ever prosecuted as they don't want any bad publicity (i .e. they just try to cover it up). If the ship has any problem with an employee they just kick him/her off the ship at the next port and send him/her home.
However, I think you are definitely safer on a cruise ship than walking around in "certain areas" of Columbus (or any other major city for that matter). Like Tibor75 I was on a cruise ship last week, I felt safe 100% of the time, and I never had any problem (except eating too much and not using enough sun screen).
Re: Of the disappearances, 12 were deemed suicides, one an accidental fall overboard, and the others were deemed "missing for unknown reasons,"
In addition, this chart (above) doesn't even list the missing persons, accidental deaths, and/or suicides for Columbus.