It had played on his mind. It had looked like a gun, but perhaps he was dreaming. The first splash was followed by a second, this time a bit closer to the dock, and then two smaller ones.

"I don't want you to go to prison, what about the baby?" the girl on the dockside had said, and the couple then vanished into the night.

The next day the man went on his holiday. He told the Police officer he had "tried to forget" what he had seen but when he arrived back in Bermuda and heard a young man had been murdered, he felt uneasy.

Trying to point out where the object had landed in the water at Darrell's Wharf, the man said the throw was roughly "from the wicket to the slips".

That was the mock briefing the Bermuda Police Service dive team had for one of their exercises, to establish their search area and pattern.

At 10.07 a.m., less than half an hour after interviewing the witness, four divers descended to scour the murky bottom.

Two set up a 'circle search' in the area where the 'gun' was thought to have hit the water. As one officer remained in a fixed position, holding the end of a rope, the other swept over the area holding on to the line in a circular movement.

He then moved one foot or so in on the rope and repeated the procedure, gradually moving inwards.

The second pair of divers decided to using a sophisticated system of roping and 'jack stays' in their search for the knife, setting up two 90 foot ropes with a 50 foot length along the bottom, weighted at both ends with the remaining 20 feet tied to buoys on the surface.

Slowly the divers moved along the distance of the rope, one on either side, hands linked together with their free hands feeling for objects embedded in the silt.

After they reached the end of each line they moved the weight to the second jack stay a few feet away and then moved back along the line to their original point, searching in a 'zig-zag' type pattern.

The gun was found more than 20 metres from the shore. Its location in the underwater crime scene was marked with a buoy — its line secured to a rock on the bottom. On the dock, a Police officer 'triangulated' the distance, using two fixed points along the dock and a laser gun to measure how far the buoy was from either side.

He then used a compass to determine the angle, noting down his measurements on a 'map' of the crime scene.

Meanwhile, the divers photographed the weapon in situ before bringing it to the surface in a plastic evidence container. It was preserved in salt water to prevent any oxidisation (rust) before forensics took over.

The gun was recovered at 10.20 a.m. and half an hour later, the second team of divers found the knife.

At 11.33 a.m. two shell casings less than an inch in size were also recovered from where they had been dropped off the side of Darrell's Wharf. At 11.40 a.m. the divers were all out of the water, having recovered the four objects dropped into the harbour — a gun, a kitchen knife and two bullet shell casings.

This was the mock crime scene in which eight Bermuda Police officers had to demonstrate their skills to UCI Founder and head instructor Mike Berry.

It was the culmination of a week of training which focused on body recovery; vehicle recovery; lifting techniques (using lift bags); communication and search patterns; and the recovery and packaging of evidence.

Among their tasks was an afternoon spent moving along a search line underwater wearing blacked-out masks, in an exercise to develop their focus in zero visibility.

Not only did the eight Police divers succeed in graduating as UCI Underwater Criminal Investigators, they also recovered eight motorbikes — most likely stolen, in the waters off Somerset.