Canada Occupational Health and Safety Regulations

18.46 (1) Subject to subsection (2), every employer shall ensure that

• (a) a diver is not allowed to approach any underwater intake or structure where underwater pressure differentials may be encountered until the flow of water is stopped or controlled; and

• (b) the flow of water is not re-established until the diver leaves the water or until the dive supervisor has determined that the diver is clear of the approach area referred to in paragraph (a).

(2) Where the flow of water referred to in subsection (1) cannot be stopped, the employer shall assess the safety of a diver approaching the intake by determining flow patterns using reliable indicators, direct measurements or calculations.