The Complete SCUBA Dive Tables Cheat Sheet: Master Decompression Planning & Safety

What Are Dive Tables and Why They Matter

Dive tables are mathematical charts that calculate safe diving profiles to prevent decompression sickness (DCS). They determine maximum bottom times, surface intervals, and repetitive dive limits based on nitrogen absorption and elimination rates. Even in the age of dive computers, understanding dive tables remains crucial for backup planning, equipment failure scenarios, and developing a deeper understanding of decompression theory.

Why Dive Tables Are Essential:

• Backup safety system when computers fail
• Foundation for understanding decompression theory
• Required knowledge for most diving certifications
• Critical for dive planning and safety management
• Universal language among dive professionals worldwide

Core Concepts and Principles

Nitrogen Absorption and Elimination

• Henry’s Law: Gas absorption increases with pressure (depth)
• Tissue Saturation: Different body tissues absorb/release nitrogen at varying rates
• Compartment Model: Body divided into theoretical tissue groups with different half-times
• Half-Time: Time required for tissue to absorb/eliminate 50% of nitrogen
• M-Value: Maximum allowable nitrogen pressure before DCS risk

Key Terminology

Major Dive Table Systems

US Navy Tables

• Depth Increments: 10-foot intervals
• Time Increments: Variable (1-10 minutes depending on depth)
• Compartments: 6 tissue groups
• Conservative Factor: Moderate
• Best For: Military/commercial diving, basic recreational training

PADI Recreational Dive Planner (RDP)

• Format: Table and wheel versions available
• Depth Increments: 10-foot intervals to 130 feet
• Time Increments: Variable based on depth
• Safety Features: Built-in safety factors for recreational diving
• Best For: Recreational diving, certification courses

NAUI Tables

• Approach: More conservative than US Navy
• Flexibility: Allows for various safety factors
• Integration: Works with NAUI training materials
• Best For: Recreational diving with conservative approach

Step-by-Step Dive Planning Process

Single Dive Planning

Step 1: Determine Maximum Depth

• Round up to next 10-foot increment on table
• Example: 67 feet = use 70-foot row

Step 2: Find No-Decompression Limit

• Locate depth row, find maximum bottom time
• Example: 70 feet = 50 minutes maximum

Step 3: Plan Actual Bottom Time

• Choose time well within limits for safety margin
• Account for air consumption and dive objectives

Step 4: Determine End-of-Dive Pressure Group

• Cross-reference depth and actual bottom time
• Note pressure group letter for surface interval planning

Repetitive Dive Planning

Step 1: Calculate Surface Interval

• Use previous dive’s ending pressure group
• Find minimum surface interval for desired new pressure group
• Longer surface intervals = lower residual nitrogen

Step 2: Determine Residual Nitrogen Time (RNT)

• Use new starting pressure group
• Find RNT for planned repetitive dive depth
• This represents “penalty time” from previous diving

Step 3: Calculate Adjusted No-Decompression Limit

• Subtract RNT from original NDL for planned depth
• Formula: Adjusted NDL = Original NDL – RNT

Step 4: Plan Repetitive Dive

• Bottom time must not exceed adjusted NDL
• Total nitrogen time = RNT + Actual Bottom Time

Common Dive Table Formats and Usage

Table Format

Depth (ft) | 10 min | 20 min | 30 min | 40 min | NDL
-----------|--------|--------|--------|--------|----
60         |   A    |   B    |   C    |   D    | 55
70         |   B    |   C    |   D    |   E    | 50
80         |   C    |   D    |   E    |   F    | 40
90         |   D    |   E    |   F    |   G    | 30

Wheel/Calculator Format

• Outer Ring: Depths and bottom times
• Inner Ring: Pressure groups and surface intervals
• Advantage: Faster calculations, visual reference
• Disadvantage: Less precise than tables

Safety Rules and Limitations

Universal Safety Rules

1. Ascent Rate: Never exceed 60 feet per minute (1 foot per second)
2. Safety Stop: Always perform 3-5 minute stop at 15-20 feet
3. Conservative Planning: Stay well within no-decompression limits
4. 18-Hour Rule: Consider any dive within 18 hours as repetitive
5. Flying Rule: Wait 12-18+ hours before flying after diving

Critical Limitations

Common Challenges and Solutions

Challenge 1: Table Reading Errors

Problem: Misreading depth/time intersections Solutions:

• Double-check all calculations
• Use finger to trace rows and columns
• Have buddy verify critical calculations
• Practice with various scenarios

Challenge 2: Multi-Level Dive Planning

Problem: Tables assume square profiles (constant depth) Solutions:

• Use deepest depth reached for entire dive
• Apply 120-rule: Depth + Time should be ≤ 120 for safety
• Consider dive computer for complex profiles
• Plan conservative multi-level profiles

Challenge 3: Surface Interval Management

Problem: Insufficient surface intervals between dives Solutions:

• Plan longer surface intervals than minimum required
• Use surface interval to off-gas more nitrogen
• Consider activities that enhance circulation
• Stay hydrated and avoid alcohol

Challenge 4: Emergency Decompression

Problem: Accidentally exceeding no-decompression limits Solutions:

• Know emergency decompression procedures
• Carry emergency ascent reference cards
• Understand required stop depths and times
• Seek immediate medical evaluation after emergency ascent

Best Practices and Pro Tips

Planning Best Practices

• Plan the Dive, Dive the Plan: Stick to predetermined profiles
• Conservative Factors: Add 10% safety margin to all calculations
• Backup Planning: Always have contingency plans for problems
• Team Coordination: Ensure all divers use same table system
• Documentation: Log all dives with complete profile information

Calculation Tips

• Round Up: Always round to next deepest/longest table value
• Start Conservative: Begin with shorter times, build experience gradually
• Track Pressure Groups: Maintain awareness of nitrogen loading throughout day
• Surface Interval Optimization: Plan activities and timing between dives

Equipment Integration

• Waterproof Tables: Carry laminated reference cards underwater
• Dive Computer Backup: Use tables as backup to electronic planning
• Slate Planning: Write key numbers on underwater slate
• Surface Support: Have detailed dive plan with surface support team

Advanced Concepts

Altitude Diving Adjustments

• Reduced Atmospheric Pressure: Requires table modifications
• Altitude Categories:
  • 1,000-3,000 feet: Minor adjustments
  • 3,000-8,000 feet: Significant modifications required
  • Above 8,000 feet: Specialized tables needed

Special Exposure Considerations

Nitrogen Narcosis Management

• Depth Thresholds: Noticeable effects typically begin at 100+ feet
• Individual Variation: Effects vary significantly between divers
• Table Integration: Consider reduced bottom times at narcotic depths
• Skill Degradation: Account for impaired decision-making abilities

Emergency Procedures

Omitted Decompression

1. Immediate Actions: Return to 15 feet if possible within 5 minutes
2. Decompression Protocol: Perform 15 minutes at 15 feet minimum
3. Surface Monitoring: Watch for DCS symptoms for 24 hours
4. Medical Consultation: Contact DAN or medical professional

Table Calculation Errors

1. Discovery Underwater: Surface safely using most conservative estimate
2. Post-Dive Realization: Extend surface interval before next dive
3. Documentation: Record actual profile for future reference
4. Learning: Review calculation process to prevent recurrence

Resources for Further Learning

Essential References

• PADI Open Water Manual: Comprehensive recreational diving foundation
• US Navy Diving Manual: Authoritative technical reference
• DAN Research: Latest decompression research and safety data
• Rubicon Research Repository: Historical diving research database

Training Organizations

Online Resources

• DAN (Divers Alert Network): Safety research and emergency services
• NOAA Diving Program: Scientific diving protocols
• Navy Experimental Diving Unit: Decompression research
• Rubicon Foundation: Historical diving documents and research

Recommended Apps and Tools

• Dive Log Software: Electronic logbook with table integration
• Decompression Apps: Mobile table calculators and planners
• Dive Planning Software: Advanced profile planning tools
• Emergency Contact Apps: DAN emergency numbers and procedures

Certification Pathways

• Open Water: Basic table introduction and usage
• Advanced Open Water: Multi-level and repetitive dive planning
• Rescue Diver: Emergency procedures and problem management
• Divemaster: Teaching others and advanced planning skills
• Technical Diving: Advanced decompression theory and mixed gases

Remember: Dive tables are mathematical models with built-in assumptions. Always dive conservatively, maintain proper training, and use tables as part of a comprehensive safety system that includes proper equipment, buddy procedures, and emergency planning.