Why safe navigation is about where you refuse to go — not where you intend to pass
Contents
Use the links below to jump to any section:
- What a No-Go Area Really Is
- Why Most Groundings Occur Inside the “Planned” Track
- Safety Margins: The Difference Between Legal and Safe
- Horizontal vs Vertical Margins
- Depth-Based No-Go Areas
- Lateral Margins and the Illusion of the Centreline
- Dynamic Margins: When the Sea Shrinks
- No-Go Areas in Confined and Pilotage Waters
- How No-Go Areas Fail in Practice
- Professional Margin Thinking on the Bridge
1. What a No-Go Area Really Is
A no-go area is not simply shallow water on a chart.
It is any area where, if the ship enters it, recovery is unlikely or impossible before contact.
That includes areas that are:
- too shallow
- too close to danger
- too narrow for manoeuvre
- unforgiving of human or system error
A no-go area is defined by consequence, not just depth.
2. Why Most Groundings Occur Inside the “Planned” Track
Many groundings occur on voyages where the planned track itself was technically safe.
The failure lies in assuming that the line is the safety margin.
It is not.
The ship is not a point.
Navigation systems are not perfect.
Humans do not steer flawlessly.
Safety exists in space, not lines.
3. Safety Margins: The Difference Between Legal and Safe
Legal clearance and safe clearance are not the same.
Charts and regulations define minimums.
Professional navigation defines buffers.
Margins account for:
- position uncertainty
- steering error
- sensor error
- human delay
- environmental effects
If a plan relies on minimums, it relies on perfection.
Perfection does not exist at sea.
4. Horizontal vs Vertical Margins
Safety margins exist in two dimensions.
Vertical margins relate to depth and under-keel clearance.
Horizontal margins relate to distance from danger.
Both matter equally.
A ship with adequate depth but no lateral room can still ground during a minor alteration or yaw.
A ship with lateral room but insufficient depth can ground without warning.
Ignoring either dimension creates blind risk.
5. Depth-Based No-Go Areas
Depth-based no-go areas are usually defined using a safety depth or safety contour, not charted depth alone.
This depth must account for:
- draft
- squat
- wave response
- heel
- chart accuracy
Once defined, any area shallower than this depth becomes forbidden, regardless of how attractive it looks on the screen.
Safe water is defined mathematically first — visually second.
6. Lateral Margins and the Illusion of the Centreline
Navigators often feel safe when the ship is “on the line.”
This is an illusion.
The centreline is not protection.
It is merely the midpoint between hazards.
True safety exists in the distance to the nearest danger, not the neatness of the track.
A good plan ensures that even if the ship drifts off track, it still remains in safe water long enough for correction.
7. Dynamic Margins: When the Sea Shrinks
Safety margins are not fixed.
They reduce when:
- speed increases
- wind increases
- current strengthens
- visibility degrades
- workload rises
A margin that is adequate at 10 knots in daylight may be inadequate at 14 knots in rain at night.
Professional navigators adjust margins dynamically — they do not assume the plan is eternally valid.
8. No-Go Areas in Confined and Pilotage Waters
In confined waters, no-go areas dominate decision-making.
Channels, bends, and berths leave little room for recovery. This means no-go areas often extend well beyond charted dangers.
In pilotage waters, the presence of a pilot does not reduce no-go areas. It often increases them, because speed and proximity increase consequence.
Margins protect against misunderstanding, not just misnavigation.
9. How No-Go Areas Fail in Practice
No-go areas fail when:
- they are not clearly defined
- they are too tight
- they exist only in one person’s head
- they are overridden for convenience
- alarms are ignored or set unrealistically
A no-go area that cannot be violated without immediate alarm is effective.
A no-go area that relies on vigilance alone will eventually be crossed.
10. Professional Margin Thinking on the Bridge
Professional navigators think in terms of escape time.
They ask:
“If something goes wrong right now, do we still have room to recover?”
If the answer is no, the ship is already operating too close to danger — even if nothing has gone wrong yet.
Margins are not pessimism.
They are respect for reality.
Closing Perspective
No-go areas are the invisible walls that keep ships afloat.
They are not created to restrict navigation, but to buy time when humans or systems fail.
A plan that looks safe but leaves no margin is not conservative.
It is fragile.
And fragile plans break at sea.
Tags
no-go areas · safety margins · passage planning · grounding prevention · bridge navigation · maritime safety