Scuba Diving Basics (Recreational)

Delimitation
Always stay within the no-decompression limit and never enter an overhead enviroment. These rules make sure that you can always ascend straight to the surface, but stay below the max. ascend rate.

Technical diving ▼

In technical diving you go beyond those recreational limits.

Equipment
Primary:

  • Mask (+ Hood)
    • Types: Half mask and Full face mask (Ear equalizing via nose plugs/block/pinchers)
    • Attention: Never use Goggles for diving
  • Fins (+ Boots)
    • Types: Open heeled vs. Closed heeled, Paddle vs. Split
  • Suit
    • Types: Wet (Warm water) vs. Dry (Cold water, For thermal protection not buoyancy control)
  • BCD (Buoyancy Control Device)
    • Types: Jacket-Style vs. Wing-Style (+ Harness, Backplate)
  • Regulator (Open-Circuit)
    1. First-Stage
      • Connection to the tank
      • Reduces the pressure
      • Types: Yoke vs. DIN
    2. Primary-2nd-Stage
      • You are breathing from its mouthpiece
    3. Secondary-2nd-Stage
      • As a backup for yourself if your Primary-2nd-Stage failes
      • As a backup for your budy if his 1st-Stage failes (Air Sharing)
      • Also called Octopus
    4. Pressure-Gauge
      • Shows the pressure within the tank and your depth
    5. Inflator-Hose
      • Gets connected with the BCD for its inflation
  • Tank
    • Contains the breathing gas
    • Nomally just one and on the back
    • Consists of aluminum or steel
  • Weights
    • Ideally just enough to stay down even with a nearly empty tank
    • Normally attached as a belt or in the pockets of the BCD
    • Keep in mind that your BCD still needs to be able to lift you!

Additional: Computer, Buoy, Snorkel, Knife, Flashlight

Technical diving ▼
  • Prefer Wing-Style BCD over Jacket-Style BCD
    –> For a better trim in the water (Prone position)
  • Some prefer Closed-Circuit-Rebreather over Open-Circuit
    –> Less gas consumption and No bubbles
  • Carrying multiple tanks instead of just one
    –> Longer and/or deeper dives possible
  • Carrying backups of the important gear
    –> To survice in case of a failure
  • Using special gear like a guide line (on a reel)
    –> To find the return way out of a cave/wreck
Commercial diving ▼
  • Use helmet instead of mask
  • Get breathing gas via hoses
  • Carry tank just as backup

Checking
– 1st: Site (Current, Exits)
– 2nd: Gear (BAR, Buddy)

BAR:
B –> Boyancy (Infalte/deflate BCD, Check weights)
A –> Air (Breath on Primary-/Secondary-Second-Stage)
R –> Releases (Check on BCD, Tank and Belt)

Basic Skills
– Dive Planning (Tables/Computer)
– Setting Up the Gear
– Cleaning the Gear
– Hand Signals
– Backward Roll Entry
– Negative Buoyant Entry
– Buoyancy Control / Trim
– Finning Techniques
– Regulator Recovery
– Mask Replacement
– Air Sharing1
– Buddy Breathing2
– Deploying a DSMB
– Safety Stop

1) You and your buddy breathing parallel from one breathing gas source.
2) You and your body breathing alternating from one breathing gas source.

Technical diving ▼

You have to know and train way more skills, like Valve shutdown drills, Decompression stops, Switching breathing gases. For Cave and Wreck penetration diving you also have to learn skills, as Line laying and Light signals.

Descend and Ascend
On the Surface always infalte the BCD.
– Descend: Defalte BCD, Pressure Equalizing (Ears, Mask)
– Ascend: Deflate BCD, Max. speed is 10m/min, Safety Stop (3min on 5m)
– Emergency Ascent: Exhale until Surface

Buoyancy and Trim
– Buoyancy: Number of Weights, BCD Inflation
– Trim: Position of Arms and Legs, Weights and Tank

Finning and Maneuvering
– Finning: Flutter Kick, Frog Kick, Scissor Kick, Dolphin Kick (Monofin)
– Maneuvering: Helicopter, Rolls

Disorders
– Barotrauma: Happens if you can’t equalize while descending or without breathing while ascending
– Decompression Sickness: Happens if you ascend too fast with too much inert gas3 in your tissues
– Nitrogen Narcosis: Happens if you are too deep with too much nitrogen
– Oxygen Toxicity: Happens if you are too deep with too much oxygen

3) For Air/Nitrox it’s Nitrogen

Breathing Gas
Atmospheric Air:
– Consistency: ~21% Oxygen, ~79% Nitrogen
– Specifics: Standard Gas, Benefits Decompression Sickness and Nitrogen Narcosis

Enriched Air Nitrox:
– Consistency: More Oxygen (default: 32% or 36%) and less Nitrogen then Air
– Specifics: Extends the No-Deco Limit, Reduces the MOD, Benefits Oxygen Toxicity

No-Deco Limits:

Depth Air (21%) EAN (32%) EAN (36%)
15m 100min 200min 310min
18m 60min 100min 100min
22m 50min 60min 60min
25m 40min 50min 60min
28m 30min 40min 50min
31m 25min 30min 40min
34m 20min 25min 30min
37m 15min 25min –
40m 10min 20min –

Source: NOAA Diving Manual 4th Edition

Technical diving ▼

– Depending on the depth you have to reduce O and N, to reduce Oxygen Toxicity & Nitrogen Narcosis
– Gas mixtures for deeper dives: Trimix (O,He,N), Heliox (O,He), Hydreliox (O,He,H) and Hydrox (O,H)
– For decompression dives EAN gets used during the deco to accelerate it (reduces the deco time)

Types of Oxygen-Level:
1. Hyperoxic (O > 21%) : Tx 30/30 (30% Oxygen, 30 Helium, 40% Nitrogen) –> MOD 33m
5) Normoxic (18% ≤ O ≤ 21%) : Tx 21/35 (21% Oxygen, 35% Helium, 44% Nitrogen) –> MOD 45m
6) Hypoxic (O < 18%) : Tx 15/55 (15 Oxygen, 55% Helium, 30% Nitrogen) --> MOD 75m

Hints
– For better visibility put soap or spit into your mask a little while before you go diving
– To prevent pain don’t go diving if you have a cold, cause you can’t equalize ears and mask