Question: Is clearing water from a mask an example of something you need to know in order to be scuba diving certified?
About the article "Scuba diving", section "Scuba diver training and certification".

Candidate passages:
Advanced Open Water Diver (AOWD) is a scuba diving certification level provided by several diver training agencies, such as Professional Association of Diving Instructors (PADI), and Scuba Schools International (SSI).
The equivalent course offered by National Association of Underwater Instructors (NAUI) is the Advanced Scuba Diver.
The certification level is roughly equivalent to the CMAS * Diver qualification and the British Sub-Aqua Club (BSAC) Ocean Diver qualification, although some differences occur.
For example, BSAC Ocean Divers are trained in the use of Nitrox and basic rescue skills for recreational diving.
The SSI Advanced Open Water program is different from most other organizations, as they require not only training but they also require diving experience.
To be certified as a SSI AOWD one needs to have completed four specialty courses and minimum of 24 logged dives.
In the absence of a logged dives requirement, it is possible to become certified as AOW with some other agencies while having less than 10 lifetime dives.
Scuba Diving International (SDI) offers an Advanced Adventure Diver course similar to the Advanced Open Water Diver Course offered by the Agencies noted herein. 
  Hip boot – Hip boots, or waders as they are colloquially called, are a type of boot initially designed to be worn by river fishermen.
Waders (footwear) – Waders refers to a waterproof boot extending from the foot to the chest, traditionally made from vulcanised rubber, but available in more modern PVC, neoprene and Gore-Tex variants.
Diving mask – A diving mask is an item of diving equipment that allows scuba divers, free-divers, and snorkelers to see clearly underwater.
Wetsuit – A wetsuit is a garment, usually made of foamed neoprene, which is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports, providing thermal insulation, abrasion resistance and buoyancy.  
SCUBA equipment is not commonly used in civilian commercial diving, but is often employed by scientific, media and military divers, sometimes as specialized equipment such as rebreathers, which are closed circuit SCUBA equipment that recycles breathing gas instead of releasing it into the water.
It is the "re-breathing" of gas that makes rebreathers ideal for long duration dives, efficient decompression when the gas mix is adjustable, and for the observation of animals in the wild due to the lack of noisy bubbles.
These characteristics also make rebreathers ideal for military use, such as when military divers are engaged in covert action or when performing mine clearance where bubbles could potentially set off an explosion.
Open circuit scuba equipments are occasionally used by commercial divers working on sites where surface supplied equipment is unsuitable, such as around raised structures like a water tower, or in remote locations where it is necessary to carry equipment to the dive site.
Normally, for comfort and for practicality, a full face mask such as those manufactured by Kirby Morgan will be used to allow torches and video cameras to be mounted onto the mask.
The benefit of full-face masks is that they can normally be used with surface supplied equipment as well, removing the need for the diver or the company to have two sets of expensive equipment. 
Most entry-level training is similar across the diver training agencies, although some may emphasize certain topics earlier in the program, such as the inclusion of diver rescue in syllabuses such as CMAS 1* and NAUI, and its absence from other equivalent courses such as PADI.
Basic diving theory: * Diving physics * SCUBA Equipment * Human physiology * Diving hazards and precautions * Diving signals * Buddy system  Basic water skills: * Finning and mobility in-water * Fitting and wearing a diving mask * Snorkeling * Shallow free-diving * Entering and exiting the water (seated entry, ladder exit, giant step entry, etc.)
Snuba is a form of surface-supplied diving in which an underwater breathing system developed by Snuba International is used.
The word Snuba is a portmanteau of "snorkel" and "scuba".
The swimmer uses swimfins, a diving mask, weights, and diving regulator as in scuba diving.
The air, however, instead of coming from tanks strapped to the diver's back, comes through a long hose from tanks on pontoon rafts on the surface (which is different from Hookah diving, where air is generally supplied with a gas-powered air compressor).
Snuba often serves as a form of introductory diving, in the presence of a professional, insured guide, and following a half-hour lesson (but not requiring scuba certification).