Most of us only hear about the work of police underwater units when theres a highly publicised search for a missing person. Searching for and recovering bodies is all part of the job for a police diver, but as I discovered, it forms only a small part of a very demanding and interesting job.

The Avon & Somerset Underwater Search Unit comprises nine active divers at any one time with three others in reserve. While always on call, the team divides its time between diving operations and its wider role as part of the Avon & Somerset Constabulary Support Group. This can range from such duties as policing demonstrations and football matches to giving talks to local schools and groups.

Financial cutbacks have hit the police force along with all other areas of public spending, resulting in several of the smaller underwater search units being disbanded. Because of these cutbacks, the Avon team also works under contract to other forces, principally Gloucestershire, Dorset, and Wiltshire. As with all other forms of commercial diving, the police teams standards of training and operation are set by the Governments Health and Safety Executive. The yearly medical and fitness assessments are comprehensive and failure means an instant suspension from diving, so a certain amount of provision is made within the support group for physical training.

New recruits to the team are only taken on from within the police force, ensuring that they are first fully trained as police officers and then as divers. After undertaking basic pool assessments locally, successful applicants attend an initial 8-week training course at one of the national police diving schools run by the Strathclyde and Northumbria forces. The courses are run to HSE training standards and successful candidates are awarded a special HSE Part 3 (Police) certification. This recognises the fact that police divers are trained to a very high standard in search and recovery techniques, while they are not trained in underwater welding and engineering skills applicable to most other areas of commercial diving.

Equipment used is based on the assumption that all water is contaminated in some way - a fair assumption when your favourite dive sites are docks, sewers and industrial culverts! Drysuits and Aga MK11 full face masks are standard kit. The Aga masks are ideal for this type of diving as they operate on a positive pressure system, meaning that any leak on the face seal only results in air leaking out and not water leaking in.

At depths down to 30m divers use the standard Aga backmount system, comprising twin 4-litre, 300 bar, tanks. This gives a very small, low-profile tank system, although it is not particularly light. Below 30m HSE regulations dictate the use of surface demand systems, so when diving this configuration the Aga sets are used as a bail-out system.

Divers are always connected to surface by a lifeline, so no BCs are used. This is partly to reduce the risk of snagging on underwater obstructions and partly because a diver involved in a fingertip search has no need to stay off the bottom. The lifeline also carries in its core a communications cable, enabling the diver to be in constant voice contact with his handler on the surface.

The Amron system used by the Avon force uses a combined transmit and receive transducer located on the bone behind the divers ear. While in constant contact with the surface, divers are not in direct contact with each other. However, the use of full face masks which have a large air-filled oral-nasal cavity, rather than a standard regulator held in the teeth, enables divers to shout at each other under water!

The teams 6-wheel-drive, Stonefield dive wagon carries all the equipment, a 7cfm Bauer compressor and the all important tea-making facilities. A familiar and distinctive sight rumbling round the roads of Bristol, this rather aging transport is about to be replaced by a brand new purpose-built diving wagon. A Mercedes turbo-diesel on a fire engine chassis will form the basis for the new truck. Gear storage and wet and dry areas inside will include a small kitchen area as well as a shower and toilet. An external shower will be used for decontamination after particularly nasty dives. Backing up the mobile unit the group has a second Bauer compressor located back at headquarters.

So far as water-borne transport is concerned, the roof of the Stonefield is home to a small Zodiac inflatable with a larger 6m Delta RIB being towed when required.

Despite being equipped for most eventualities, the majority of the teams jobs dont require anything as complicated as a boat. Some of the jobs dont even require diving: just the protection afforded by drysuits and full-face masks. The teams responsibilities include security searches of drains and sewers along routes to be taken by visiting royalty and other dignitaries. While not under water, the full kit is worn on these jobs to combat the pollution risk and make the job slightly less unpleasant.

This ability to work unhindered by smell and infection has not gone unnoticed by other areas of the force. Consequently, police divers are now routinely called upon to deal with cases involving badly decomposed bodies, which can present a health risk to those who have to deal with them.

Routine training dives often take place at popular dumping grounds for stolen goods. Bridges, canal towpaths and the Bristol docks all look like good places to lose things forever, but thieves beware: these are just the places where our police friends go to play.

While I was with them they were called on to search a particularly nasty-smelling culvert round the back of the Avonmouth sewage works. It was believed that some stolen mailbags had been dumped there, and these were duly recovered. In the process they also recovered a set of alloy car wheels and a motorcycle frame.

Stolen goods, weapons, even vehicles and sometimes the most unlikely objects are all recovered from some pretty obscure places. Take for example the two bodies recovered from a river in Somerset. A late-night motorist reported having witnessed two men dumping two large, body-sized objects off a bridge into a Somerset river.

The diving team was duly called in to search the area below the bridge, and indeed found two large objects wrapped in polythene. After taking them to the bank, further investigation revealed that they were bodies, not of humans, but of goats! And even more bizarrely, both had apparently been used in some black magic rite and been ritually mutilated.

What do the team do when they are not working Well obviously, like any sane person they go diving! The Avon & Somerset Constabulary has for the past two years had its own BSAC special branch. Open to full-time and civilian members of the force, it currently has 10 active members and ensures that the diving team dont get withdrawal symptoms when off duty.