312.23. Voice communication system: In addition to the system referred to in section 312.22, a 2-way voice communication system between the diver underwater and the dive team members on the surface must be used for all dives(1) that are surface-supplied;
(2) with a buddy and free-swimming;
(3) at the end of submerged pipes;
(4) in an environment with an obstruction;
(5) in a restricted access area;
(6) under ice;
(7) in a contaminated environment; and
(8) to a depth of more than 40 m in the case of a police dive when the location does not allow the transportation of a hyperbaric chamber to the diving station.
During a dive to a depth of more than 50 m, the 2-way voice communication between the diver and the surface must be recorded for the entire dive. The recording must be kept for at least 48 hours.
A dive must be interrupted if the 2-way voice communication system should fail.