Diving Operations

The diving survey was split in two units of 15 days with a six day break in between and took place between 4 July and 8 August 2005. Again MV Flatholm of Coastline Surveys was used as support vessel. The project staff consisted of five archaeologists and three crew aboard MV Flatholm. The archaeological team consisted of four divers and an archaeological recorder. Diving roles were rotated within the team. Two divers were appointed as diving supervisors.

All dives were conducted using surface supplied diving equipment with Kirby Morgan 28 band masks.

The diving panel, communication box and video recording equipment were set up in the survey container next to the recording computers and the SCOUT system. The air supply consisted of five 300bar J-bottles secured to the outside of the survey container. After each dive the cylinders were recharged using an onboard diesel HP compressor.

On the starboard side of the vessel a gate was cut into the rail to provide safe access to the water via a diving ladder. The umbilicals were stowed on the open working deck.

The dive team generally consisted of diving supervisor and recording system operator in the survey container, standby diver and tender on deck and one diver in the water. On some of the shallower sites the standby diver was used in-water alongside the main diver to aid with recording or to obtain digital video and stills footage of the main diver.

Every dive was recorded on miniDV tape using a colourwatch digital video system with hat mounted camera. A Canon Powershot G2 in Ikelite housing with Ikelite DS 125 substrobe was used to take digital still photographs. A .56 Sea and Sea wide-angle lens allowed the photography of larger objects from close distances.

On night dives and deeper sites with low visibility a 100 Watt Lumb Bros FIII underwater torch was employed.

In addition to the diver recording system based on acoustic tracking, conventional recording methods, such as offset drawing, were used on the dived wreck sites.

Depending on the desired level of recording, underwater photography, videography, sketches and drawings were used. Trilateration and offset measurements were acquired with folding rules or tape measures.

You can see how the methods worked by looking at the Bottle Wreck. This wreck was recorded using traditional marine archaeologcial methods. A 32m by 10m grid was established around the visible remains of shipwreck and cargo. The pipe cargo mound and individual artefacts were then drawn in relation to the grid using offset and trilateration methods. To link the site grid to real world co-ordinates accurate fix points were taken for each of the grid corner points with the USBL system. To speed up the drawing and recording process, measurements were obtained by the diver, but the drawing was carried out by the supervisor on the surface. This was done using the live video link provided by the colourwatch system.