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Snorkel Diver

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  1. Snorkel Diver

  2. Benefits of BSAC membership • The organisation • International recognition • Support materials • Snorkelling is fun

  3. Basic Equipment

  4. Basic Theory • Pressure • Breathing • Buoyancy • Buoyancy Aids

  5. THE EFFECTS OF PRESSURE Atmospheric Pressure = Weight of air in a 1 cm square column of the atmosphere = 1kg / cm2 = 1 bar

  6. THE EFFECTS OF PRESSURE Water pressure SEA LEVEL 1.0 bar 2.0 bar 3.0 bar 4.0 bar 5.0 bar 10m 20m 30m 40m Pressure of water = approx. 1 bar every 10 metres

  7. GASES UNDER PRESSURE Volume Absolute Pressure 1 bar AIR Depth 0m 10m 2 bar 1/2 20m 3 bar 1/3 30m 4 bar 1/4

  8. GASES UNDER PRESSURE Volume • Air space compression on • descent, expansion on ascent • Equalisation of pressure in • flexible body air spaces • Avoid pressure damage • never hold breath during • ascent • Breathe normally during • ascent

  9. BODY AIR SPACES Sinuses Middle ear Airways Lungs Gut

  10. EFFECTS OF COMPRESSION The Ear Outer ear Inner ear Ear drum Middle ear Eustachian tube

  11. EFFECTS OF COMPRESSION Pressure on the ear Normal External pressure Reversed ear • Prevent discomfort by ‘ear clearing’

  12. EFFECTS OF COMPRESSION Sinuses Air spaces • Do not dive with a cold

  13. EFFECTS OF COMPRESSION Lungs and Airways Mask squeeze Airways Heart Lungs

  14. EFFECTS OF COMPRESSION Breath-holding diving 0m At 30m, lung volume is compressed to ¼ of normal volume

  15. BUOYANCY Empty lungs Full lungs Normal breathing Positive Neutral Negative

  16. SENSES UNDERWATER Focusing of the eye in air and underwater Water Air Actual image Apparent image Refracted rays pass from water to air

  17. SENSES UNDERWATER Focusing of the eye in air and underwater Water Air Actual image Apparent image Refracted rays pass from water to air

  18. SENSES UNDERWATER Absorption of colour underwater RED BLUE GREY GREEN YELLOW ORANGE 5m 10m 15m 20m 25m 30m

  19. SENSES UNDERWATER Sound • Sound passes through • water four times faster • than through air • Difficult to judge direction • of sound underwater

  20. Basic Theory • Pressure • Breathing • Buoyancy • Buoyancy Aids

  21. Safe Snorkelling • Choice of Site • Conditions • Buddy - Group • Dive Plan • Protective Clothing • Marine Life • Snorkelling is Fun