Two teenagers were hit in Maunalua Bay on Oahu island, in Honolulu’s Hawaii Kai area.
They were hauled from the sea and taken ashore by a fishing boat. One, Keahihoku Lum, aged 17, died in hospital.
The surviving diver later told of a speeding vessel which ran over the pair, despite their having towed a float with diving flag.
A local dive centre operator told press that divers in the bay regularly tow surface flags to indicate their positions.
Divers sometime venture near a channel used by boats from a nearby marina. But under state law, boats should avoid diving flags at all times.
Boats should not approach within 30m of a diving flag, and should slow to a speed which puts out a negligible wake once within 60m.
"Many boats leave the marina far faster than the 5mph posted,” said a local canoe club coach. “We as canoe paddlers are always aware of that."
The boat involved was identified as an 8m powerboat, owned by a 32-year-old who was at the helm.
Criminal charges could follow.
Related links
Collision diver returns home (June 09)
Prop kills diver (March 09)
Boat injures diver (Feb 09)
Divers killed beneath jetty (April 08)