Deja vu all over again?
"Alpha flag is required in Federal waters if maneuverability is restricted by diving activities."
In the 80's an experienced diver, IIRC an instructor, was seriously injured when the dive boat ran over him with their prop. Part of the resulting debate was whether it could ever be considered safe to operate the engine while divers were in the water, period. This was in NY, where the norm was for a dive boat to anchor--even when that meant anchor in a wreck 100+ feet down. It was seriously under consideration that the engine key should go down with a diver, leaving only a spare "in case of emergency break glass" key on board, to guarantee there could be no accidents.
Florida? I heard a USCGAux member discussing lost divers, and he said there are SAR missions being run literally every day in Florida, for lost divers and boaters. Maybe it is time for the various associations (boat owners, tourist orgs, chambers of commerce, etc.) to consider doing what others have done for years in other places: Put out a mooring buoy. A big heavy mooring buoy. And that way, at least the dive boat will be in a predictable location when the divers go looking for it.
Lookouts and SMBs and all the rest, just isn't working. Time to look for other solutions.