This is something to keep an eye on with your cylinders. If it occurs it can make the cylinder very difficult to service and even reduce the cylinders ability to function correctly.

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Listed underneath Table 3 of your PADI or on the inside lid of your eRDPml is listed Special Rules for Multiple Dives.

This states that when planing 3 dives or more any dive ending in pressure group Y must have a 3-hour surface interval. This then applies to all subsequent dives in that sequence.

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The phenomenon of light bending obliquely as it passes through mediums of different densities is called refraction. This can be observed when viewing an object through a glass of water.

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Tidal Volume represents the normal volume of air displaced in the lungs with inhalation and exhalation without any additional effort. Any air in the upper respiratory tract not involved in the exchange is referred to as Dead Air.

This is increased with the use of a snorkel and regulator which is why it's so important to breathe in a full, relaxed manner to ensure exhaled air has cleared the increased dead air space.

The answer to this can be found in your PADI Instructor Manual in the Paperwork and Admin Procedures section under the heading Knowledge Development Assesment.

Each incorrect answer should be reviewed after completion of any Knowledge Development, Quiz, Quick Review and Exam and retesting should happen for those scoring less than 75%.