My son and I were on the boat when this incident happened. The report mentioned above from the Miami Herald is very accurate. Some details as we saw them. This accident happened at the end of the second dive, at French Reef. There was a fairly strong wind, and 2 - 3 foot waves. There WAS a slight current. The boat was moored downwind and current from the reef. The pre dive briefing was very clear - swim to the reef, stay in that area, make a surface boat check after 30 minutes if unsure where the boat was (reef was 30 to 40 ft). We were told that this dive was one hour maximum. The captain and one crew member stayed on the boat.
My son and I entered the water at around 3:05. After 30 mins, I surfaced, a little unsure where the boat was, and to my surprise, saw that we were around 100 yards behind it. I then descended to my son, and we made our way back to the boat, re boarding at around 4:00. I think another group followed us after that.
At the hour mark, around 4:05, the crew counted all passengers, and found two missing. I've dived in the Keys many times, and this is hardly unusual. Divers are often five or ten minutes late. At hour mark, the captain and crew (there was another instructor who had dived) immediately began looking for the missing divers. After a short time, all passengers joined in in earnest. As stated in the Miami Herald article, the sun was low in the sky, and made searching in that direction almost impossible. EVERYONE on board scanned the sea in all directions for around 20 minutes, but with no success. The captain then notified the US Coast Guard (probably around 4:25 / 4:30)
By coincidence, a boat from the Florida Wildlife and Fisheries was nearby, although still 20 minutes away. When he arrived he immediately searched the area down wind / current of the boat, with no success. He then did a complete circle of the area, again finding nothing. With the Coast Guard boat minutes away (they came from Islamorada), he tried another sweep down wind of the boat, where on the third pass he found the divers. Unfortunately the lady had not survived. The Fisheries officer estimated (using his GPS) that they were well over half a mile from the moored dive boat, directly in line with the setting sun. It was an area that all on board had focussed on when looking for the divers.
Talking to the surviving diver on the ride back to shore, he stated that they had indeed surfaced some distance behind the dive boat, and had attempted to swim back. I'm guessing that this must have been at the end of their dive - he didn't state how long they had been down, or if they still had air. After some time, they had split up, and when he looked back, the female was not moving. He then returned to her, found that she had stopped breathing, and waited with her for rescue.
As many people have said, there are lessons to be learned from this accident. A scuba sausage would have helped. A whistle may have (not sure if they had rental gear - we did, and a whistle was attached). And as stated in the previous post, relaxing on the surface and inflating your BC would have been better that trying to swim back to the boat. I don't want to second guess the divers who were lost - who knows what was going through their minds? I know that my son and I are very fortunate - thanks to checking our location, we realized we were in the wrong spot, and managed to safely make our way back to the boat. We could easily have been in their place.
One last comment - the crew did everything that they could, and were professional and compassionate. This was an awful accident, which may have been avoidable given a few things going differently. Let's learn from this, and hopefully some good will come of it.
Our thoughts are with the lady's family and friends.