"The reef that Kirsty was killed on wasn't roped off, but it is subject to a speed limit and is a known diving location."

300m off the shore, IIRC 100m is the area that is normally taken to the danger zone and the speed of boats, jet-skis is restricted or subject to exclusion rules. If the area is not clearly marked then the situation created by that omission is literally a disaster waiting to happen.

The reports say that the boat was a "Speed Boat" - a day boat with no enclosed cabin so it is highly unlikely that they had a chart table or indeed a chart. The speed restriction and the fact that it was an area used by divers may, or may not have been marked on any "local" chart but that would only be "known" if that chart was available and those in the boat had the means to identify their position on that chart. Generally people are extremely poor at estimating distances and speeds at sea.

A terrible tragedy but fault does not purely lie with those on the boat. For a speed boat to run any "diver" down means that the diver would have to be on or very close to the surface. Divers, whether diving with a dive-leader or not are responsible for surfacing safely, to do that they must:
- Look up at the surface to visually check that the surface is clear.
- Listen, any power boat, particularly one moving at speed makes one hell of a din.
- Monitor the size of your exhaled bubbles and keep pace and adjust rate of ascent to match the smallest bubbles you can see.
- Hold one arm straight up so that your hand breaks surface first and keep it above your head so that the crew of your dive boat can see you, to count all members of the dive party to surface THEN to go in and recover them.

Irrespective, on a known dive location the dive leader should always run the dive so that you enter the water and descend in a safe location and surface in a safe location (Best way of doing this to surface on a "Dan-Buoy" type marker clearly displaying the international code Alpha Flag)