Viv, thanks for the link.

It goes a long way toward explaining how people could have been abandoned
for so long at such a popular site.  It also clarifies how irresponsible the
operator was in not discovering and doing something about the missing
divers.

Since this discussion started, I had a chance to talk with a local Ft.
Lauderdale Captain about his procedures and have a bit to add about how
another Keys operator tries to ensure his cutomers all return.

Local
It turns out that at least some local captains do not have a standard
procedure requiring a roll call after every dive.  The one I talked with
uses a roll call when dealing with a group he does not know but sometimes
does not do one when he believes he knows everybody aboard.  I suggested to
him that, for his own protection, he probably ought to do a roll call on
every dive.  He agreed.  My real thinking was that any time there's more
than a few people on a boat, the chances of not noticing someone you know is
not aboard is too great a risk to take.  On my boat, where there are never
more than 6 divers and rarely more than 4, it's amost impossible to fail to
notice someone is missing.  Not so on a boat designed for 20 or more divers.

Keys
Lady Cyana, an operator I've recommended to others, takes a driver's
license, passport or some similar form of identification from all divers.
Florida law requires you to have your driver's license with you when
driving, causing it to be one of the few things people remember to recover .
. . usually.  The license idea is not foolproof, but the operator also does
roll calls.

Lee