From the reading of that Google excerpt, it sounds as though a live boat dive with a flag ON the boat and the boat following divers, would not necessarily have to have a float in the water during the entire dive.
I do understand the rationale about recreational divers not having time to deploy an SMB, but if the divers are beginners enough to be likely to end up on the surface precipitously, it seems as though the boat ought to be following them rather closely.
Not criticizing. Just seems like a setup for difficulties if you have a stiff breeze and a diver below trying to manage a flag on the surface. (We have dive sites here that have truly ferocious surface current that literally dies below 20 feet. Trying to hang onto a float under those conditions would be a bear!)
These are good questions, but in Florida it is the law to stay close to a flag. Cozumel often has crystal clear water and the divemasters kinda make the people stay in one group, the bubble plume from 10-12 divers is pretty obvious. I did a few trips to cozumel and people talked about the currents and for the most part I never saw much more than a mild current. In south Florida we can have 2-3 kt currents on the surface. Also, in my diving in cozumel, you are diving a wall or a relatively narrow reef line, so the operator knows the divers should be popping up somewhere on a certain LINE.
An operator in Florida who drops 10-12 20 people on one spot has no way to track all the divers. Without floats, the divers can be spread all over the area. Do the math.. 45 minutes in the water 2-3 kt current, the dive will cover over 1 mile of reef. If some divers stop and do macro and only move 150 yards and others actively swim in the water column chasing fish etc. There is no way for the boat operator to track all the divers they can easily be spread way out.
If he has at least a few float carriers within the group, he has a decent idea of where the people are, assuming that the slow group has a float and the fast group has a float. People can also swim across the current and pop up hundreds of yards inshore or offshore; they may not be located along a well described linear feature (as in say cozumel). Also, in south Florida, there are fisherman all over the place, having a float over your head provides some protection.
Yesterday, I did a drift dive with a surface current of about 3.5 kts in 185 feet, with 30 feet visibility trying to find a small plane wreck. In these conditions, it would be impractical to try to tow a float. The only practical way, is to drift into the wreck and stay on it, when you are done diving it, you then send up a marker buoy and then drift off the wreck and hope the boat is watching as you drift a mile or two on your deco. If you are drifting into a relatively small location and the operator knows where that is, he can hold station and try to notice when the surface marker hits the surface and then follow that. It also helps if he knows when to expect the float to hit the surface and if it doesn't show up when he thinks it should then he can decide to look around longer or can assume he missed the float and then begin sweeps downcurrent. There are many ways this simple system can get screwed up and sometime we kinda loose a diver for a while.
This is a little video I shot yesterday, it is kinda boring, because I was looking to document a small feature of the wreck, but the deployment of the float (around 3:15) into the current might be somewhat relevant.
12-30-11 Helldiver Wreck Jupiter.wmv - YouTube
