The short version
- Cold water rarely kills by hypothermia first. The current model has four stages: cold shock, swimming failure, hypothermia and collapse around rescue[2].
- In 187 Alaska fishing vessel sinkings, 557 of 617 crew survived (90.3%). Life rafts and, beyond 30 minutes, immersion suits separated the living from the dead[1].
- Of 204 US fishermen killed by falls overboard from 2000 to 2016, 59.3% of falls were unwitnessed[3]. None of the victims in over 200 fatal falls wore a PFD[4].
- Federal rules require an immersion suit per person on many cold-water fishing vessels, and monthly drills that include donning them[5][6].
Hypothermia is the last threat, not the first
Ask a deck crew how long a person lasts in cold water and the answer is usually a hypothermia chart. The research says most cold water deaths happen before core temperature has fallen far. A 2026 review in the Journal of Applied Physiology describes four stages: cold shock, swimming failure, hypothermia, and circum-rescue collapse[2].
Cold shock starts within seconds and can kill through inhaled water, low carbon dioxide reducing blood flow to the brain, and cardiac arrhythmia[2]. In most cold water drowning deaths, hypothermia comes after the airway has already been lost[2].
| Stage[2] | What happens | What saves the crew member |
|---|---|---|
| 1. Cold shock | Gasping, hyperventilation, inhaled water, possible arrhythmia, within seconds | A PFD or suit already on, keeping the airway clear |
| 2. Swimming failure | Cooled arm and leg muscles stop working at near-normal core temperature | Flotation, not swimming; get to the raft early |
| 3. Hypothermia | Core cooling after sustained exposure | Immersion suit, life raft, shortest time in the water |
| 4. Circum-rescue collapse | Collapse driven mainly by the sudden loss of water pressure on extraction | A rehearsed recovery and post-rescue plan |
The widely taught 1-10-1 rule is a teaching shorthand for the first three stages: about one minute to control breathing, about ten minutes of useful movement, and about an hour before hypothermia causes unconsciousness. Use it to train priorities, not to predict survival for a given person or water temperature.
What the Alaska sinkings data shows
The best operator evidence comes from NIOSH researchers who studied 187 fishing vessel sinkings in Alaskan waters from 2000 to 2014. Of 617 crew at risk of immersion, 557 survived, 90.3%, and 60 died[1].
For any length of immersion, survival was associated with getting into a life raft, sinking within three miles of shore, a sinking that was not weather-related, and working as a deckhand[1]. For immersion longer than 30 minutes, wearing an immersion suit was added to that list[1].
The study’s own conclusion
Access to well-maintained, serviceable lifesaving equipment, and the knowledge and skills to use it properly, are critical to surviving cold water immersion[1]. That is a drills and maintenance finding, not an equipment shopping list.
Falls overboard: the deaths no suit prevents
A sinking gives the crew minutes to don suits. A fall overboard gives none. From 2000 to 2016, 204 US commercial fishermen died after falling overboard, according to CDC data[3]. 121 of those falls, 59.3%, were not witnessed, and 108 of those victims were never found[3].
Drowning is the leading cause of death among US commercial fishermen, falls overboard account for about 30% of fishing fatalities, and in more than 200 fatal falls none of the victims was wearing a PFD[4]. US rules require PFDs to be carried, not worn on deck[4].
| Fatal falls overboard, 2000 to 2016[3] | Number | The gap it shows |
|---|---|---|
| Total deaths | 204 | Second leading cause after vessel sinkings[3] |
| Falls not witnessed | 121 (59.3%) | No one to raise the alarm |
| Unwitnessed victims never found | 108 | Man-overboard alarms and tethers |
| Recovered but not resuscitated | 22 of 83 witnessed falls | Recovery device and rescue drills |
For the regional picture of which fisheries lose the most crew, see the NIOSH regional summaries[8] and our Alaska fleet guide.
What the Coast Guard requires on a fishing vessel
46 CFR 28.110 requires at least one immersion suit, exposure suit or wearable PFD of the proper size for each person aboard, stowed where each person can reach it from both work station and berth[5]. The type depends on the water.
| Where the vessel operates | Vessel | Device required per person |
|---|---|---|
| Seaward of the Boundary Line, north of 32° N or south of 32° S, and Lake Superior | Documented vessel | Immersion suit or exposure suit[5] |
| Coastal waters on the West Coast north of Point Reyes, CA; beyond coastal waters in cold water; Lake Superior | All vessels | Immersion suit or exposure suit[5] |
| All other waters, including the Great Lakes except Superior | 40 feet or more / under 40 feet | Approved wearable PFD, immersion suit or exposure suit[5] |
Drills are where the Alaska finding becomes law. 46 CFR 28.270 requires drills and instruction for everyone aboard at least once a month, covering abandoning the vessel, recovering an individual from the water and donning immersion suits, among other contingencies[6]. Drills must be run as if the emergency were real, with everyone taking part and donning suits if the vessel carries them[6].
After the rescue: the medical part most plans skip
Getting a crew member back aboard is not the end of the danger. The review describes circum-rescue collapse, driven mainly by the abrupt loss of hydrostatic pressure when the person is lifted out of the water, as a stage with its own mortality risk[2]. It also notes that fewer than 10% of drowning victims present in a shockable rhythm[2].
That shapes the plan. Our recommendation, as physicians writing vessel protocols: train a gentle recovery and horizontal handling where the gear allows it, start CPR for a non-breathing casualty, get a shore physician on the line early, and write the rewarming and evacuation thresholds before the season, not during it. The first aid training duty for fishing vessels sits in 46 CFR 28.210[7], and the decision to evacuate is covered in when to medevac a seafarer.
A cold water plan in six lines
- Suits sized and reachable from both work station and berth, per 28.110[5].
- Monthly drills that include donning suits against the clock and recovering a person from the water[6].
- PFDs worn on deck, not just carried. None of the fall victims in over 200 deaths wore one[4].
- A man-overboard alarm or buddy rule, because 59.3% of fatal falls were unwitnessed[3].
- Life raft serviced and drilled. Entering a raft was linked to survival at every immersion length[1].
- A written post-rescue protocol with a physician contact, CPR and rewarming steps. See remote vessel medical planning.
Discovery Health MD writes the medical half of that plan. The chest and first aid stock sit in our ship medical chest management service, the protocols in maritime medical consulting, and scheduled analgesics in controlled substances management. For crew CPR training see our CPR, AED and first aid course, and for the fleet rules read commercial fishing vessel medical requirements. Ask a physician to review your plan.
Common questions
How long can a person survive in cold water?
It depends on water temperature, clothing, flotation and the person, which is why no single number is honest. The teaching rule is 1-10-1: about a minute of cold shock, ten minutes of useful movement, an hour to unconsciousness from hypothermia. Research shows most deaths happen in the early stages, before hypothermia[2].
What is the 1-10-1 rule?
A training shorthand for the first three stages of cold water immersion: control breathing through the first minute of cold shock, use the next ten minutes of muscle function to reach flotation or a raft, and expect about an hour before hypothermia causes unconsciousness. The four-stage model adds a fourth danger, collapse around rescue[2].
Do immersion suits actually improve survival?
Yes, for longer immersions. In 187 Alaska sinkings, wearing an immersion suit was associated with survival when immersion lasted more than 30 minutes, and entering a life raft was associated with survival at any duration[1].
Are immersion suits required on commercial fishing vessels?
On many. 46 CFR 28.110 requires an immersion suit or exposure suit per person on documented vessels seaward of the Boundary Line north of 32° N or south of 32° S, on Lake Superior, and on vessels in coastal waters of the West Coast north of Point Reyes, among others[5]. Other waters allow approved PFDs.
Do fishermen have to wear a PFD on deck?
US rules require PFDs to be carried, not worn on deck[4]. In more than 200 fatal falls overboard studied by NIOSH, none of the victims wore a PFD[4]. Wearing one is the single cheapest change a crew can make.
How often must fishing vessels hold survival drills?
At least once a month under 46 CFR 28.270, covering contingencies including abandoning ship, recovering a person from the water and donning immersion suits, run as if the emergency were real[6].
What is circum-rescue collapse?
A collapse around the moment of rescue, driven mainly by the sudden loss of water pressure on the body when a person is lifted out[2]. It is why recovery and aftercare belong in the drill, and why a physician-written post-rescue protocol matters. See when to medevac.
