Around two to six divers are called to each job which can last from several hours to several days.
The squad spends most of its time on evidential searches. Sometimes these searches involve technically difficult underwater-video work which is later used as evidence.
Divers often video bodies in the sea or river to give doctors at autopsies an accurate view of how the body was found.
Videos also enable the officer in charge of a case to see exactly what the diver sees before anything is brought to the surface. The squad focuses on recovery rather than rescue.
The Police National Dive Squad has limited places and is made up of existing police officers who have regular duties in addition to their dive work and training.