The deck-side warning signs crews miss before ships start moving
Estimated read time: 55–65 minutes
Skill level: Cadet → AB → Junior Officer → Chief Mate
Contents
- Introduction – Anchor Drag Is Rarely Sudden
- What “Holding” Actually Means
- The Cable Shape and Why It Matters
- Early Deck-Side Indicators of Drag
- Vibration, Noise, and Chain Behaviour
- Environmental Triggers That Restart Motion
- Human Error Chains in Drag Incidents
- What Deck Crew Should Report Immediately
- Why Drag Is Often Not Believed
- Key Takeaways
1. Introduction – Anchor Drag Is Rarely Sudden
When a ship drags anchor, reports often say:
“The anchor started dragging.”
In reality, drag develops gradually — and deck crews often see it first.
The problem is not detection.
It is interpretation and escalation.
2. What “Holding” Actually Means
Anchors do not lock into the seabed.
They:
- resist movement
- convert motion into soil disturbance
- rely on cable geometry
Once the cable straightens, resistance drops sharply.
Holding is conditional — not guaranteed.
3. The Cable Shape and Why It Matters
A good anchor relies on:
- a catenary (curved cable)
- weight resting on seabed
- gradual load transfer
As conditions worsen:
- curve flattens
- weight lifts
- load spikes
- anchor starts to plough
Once ploughing starts, holding is already compromised.
4. Early Deck-Side Indicators of Drag
Deck crews often notice:
- chain “singing” or humming
- rhythmic vibration
- jerking through the wildcat
- cable lifting and straightening
- brake adjustments becoming frequent
These are early warnings, not normal behaviour.
5. Vibration, Noise, and Chain Behaviour
A dragging anchor produces:
- cyclic tension changes
- audible vibration
- uneven loading
Experienced deck crew often say:
“It just felt wrong.”
Ignoring that instinct delays response.
6. Environmental Triggers That Restart Motion
Common triggers:
- wind shift
- tide change
- swell alignment
- passing traffic
Many ships drag anchor after hours of holding, when conditions change slightly.
This is why anchor watches matter.
7. Human Error Chains in Drag Incidents
Repeated investigation findings:
- early signs dismissed
- bridge reassured prematurely
- “let’s wait and see”
- too little cable paid out
- corrective action delayed
Drag accelerates faster than people expect.
8. What Deck Crew Should Report Immediately
Deck-side reports that matter:
- cable straightening
- vibration increase
- brake heating
- chain jumping on wildcat
- repeated noise changes
Reports should be descriptive, not apologetic.
9. Why Drag Is Often Not Believed
Reasons include:
- GPS lag
- slow movement
- disbelief that “good anchor” could fail
- pressure to avoid re-anchoring
The sea does not respect optimism.
10. Key Takeaways
- Anchor drag develops progressively
- Deck crews see it first
- Cable geometry tells the truth
- Early reporting prevents disasters
- Delay converts inconvenience into emergency