Module 20 - Special Situations Afloat
Flooding and Hull Breach
What you will learn
Measure whether ingress is being controlled, coordinate containment and communications, and escalate before power, buoyancy or stability is lost.
The critical flooding question is not whether a pump is running. It is whether the water level is stable or falling under the current configuration and whether the source can be bounded without exposing crew.
Raise the alarm, account for people, establish position and start the yacht's water-ingress procedure. Assign control, investigation/containment, pumps and communications. Locate the source only with safe access; electrical, machinery, contamination and entrapment hazards can make an unchecked compartment dangerous.
Use the control matched to the source: isolate a failed inlet where possible, fit the correct bung or plug, support a hose, apply an external or internal patch, or reduce the load that is opening damage. A softwood bung carried near a seacock is useful only when it fits and can be driven without worsening the fitting; it is not a universal hull-repair device.
Mark and time the water level. Pump noise, a discharge stream or a temporarily dry bilge is not enough. Compare level with pumps off and on only when safe, monitor pump strainers and power, and protect communications and essential electrical capacity. Changes of speed or heading may alter ingress on some damage, but must be tested cautiously because they can also worsen the breach, stability or navigation risk.
Prepare distress communications and survival equipment while containment is still being attempted. Escalate when ingress is not controlled, the source is unknown, structural or stability margin is degrading, essential power is threatened, or the crew cannot sustain the response. Preparing a raft is not the same as abandoning; it preserves a later option.
Worked example
A straight-sided observation point in a fictional bilge rises from 12 cm to 18 cm in six minutes. With the main pump running, it rises from 18 cm to 20 cm in the next four minutes.
- 1Before the pump, the observed depth rise is (18 − 12) ÷ 6 = 1.0 cm per minute at that point.
- 2With the pump running, the net rise is (20 − 18) ÷ 4 = 0.5 cm per minute.
- 3The pump has reduced the observed rise but has not controlled it: the level is still increasing.
- 4Do not convert centimetres per minute into litres per minute without the changing bilge cross-section and measurement geometry.
- 5Report the times, levels, pump state, source evidence and trend; bring forward distress and survival preparations while containment continues.
Sense check: A pump that halves the observed rise is helping, but 'still rising with the pump on' is the operational fact. It is not a stable bilge.
| Control question | Evidence | Escalation warning |
|---|---|---|
| Is ingress bounded? | Source identified and isolation/patch holds | Unknown or inaccessible source |
| Are pumps controlling? | Marked level stable or falling over time | Level still rising with pumps on |
| Is the yacht viable? | Buoyancy, stability, steering and power retained | List, structural movement or essential power loss |
| Can crew sustain it? | Roles, access and endurance remain safe | Fatigue, exposure or loss of communications |
Run flooding as two linked workstreams
One team is containing a failed hose while the water level continues to rise and the fixed VHF battery space is threatened.
1. Contain and measure
Isolate or plug the source, mark level and time, and monitor pump effectiveness.
2. Preserve command
Keep helm/navigation, position and an external communications path working.
3. Prepare the next state
Move portable communications and survival equipment without obstructing containment.
4. Escalate on evidence
Use the rising trend, source uncertainty, power threat and crew capacity to set the assistance threshold.
Sense check: If every person is pumping below, nobody is protecting navigation, communications or the decision to leave the compartment.
Common mistake or limitation
- Calling flooding controlled because a pump can be heard or water is discharging.
- Sending crew into an electrically, mechanically or structurally unsafe space to find the source.
- Using a bung, cushion or heading change as if it were a universal repair.
- Waiting to prepare communications and survival equipment until power or access has already been lost.
Recap
- Containment, measurement, vessel control and communications must run together.
- A marked water-level trend is stronger evidence than pump noise or intention.
- Still rising with pumps on means ingress is not controlled.
- Escalate before buoyancy, stability, power or crew capacity removes the remaining options.
Optional quick check
Section 5 of 12
The bilge level rises more slowly after the pump starts but is still increasing. What does that prove?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying Special Situations Afloat
This public lesson is part of Revision Module 20. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.