The Ultimate Life Jacket Guide

The Ultimate Life Jacket Guide

By: SamComments: 4


As sailors ourselves, we understand how paramount having the best possible safety equipment is. This safety equipment starts with the most important bit of personal equipment of them all, a life jacket.

Within this blog post we’ll be looking at the following:

We'll then round the blog post off with some of our most Frequently Asked Questions.

Inflation Types:

Automatic life jackets contain a mechanism that when wet, activates a sensor that fires and activates a gas bottle, releasing CO2 which then inflates the life jacket. If a man overboard is knocked unconscious or is disorientated, an automatic life jacket would show its worth. All automatic life jackets contain a manual pull string as a back-up.

A Hammar/Hydrostatic life jacket works in the same way as an automatic life jacket does, however the mechanism will only be activated when the sensor is a few centimetres below the water and is fully submerged. All Hammar/Hydrostatic life jackets contain a manual pull string as a back-up.

A manual life jacket will only inflate when the string is pulled, activating the sensor that fires and activates the gas bottle, inflating the life jacket. Automatic and Hammar/Hydrostatic life jackets all contain a manual pull string as a back-up.

ISO Approval:

In July 1995 a law came in that made it illegal to sell Life Jackets or Buoyancy Aids that have not been tested to European or International specifications.

All of the life jackets we sell have the relevant CE or ISO marks.

So what are the four main classifications for ISO Approval?

ISO StandardCovered ByLevel of Buoyancy Provided
ISO12402-550N Buoyancy Aids5KG
ISO12402-4100N Life Jackets10KG
ISO12402-3150N Life Jackets15KG
ISO12402-2275N Life Jackets27.5KG


Life jacket buoyancy is measured in Newtons (N). 10 Newtons = 1KG of Buoyancy. The amount of buoyancy required comes down to two major factors:

  • Where you are.
  • What you are wearing.

Here is a simple breakdown of the different buoyancy standards:

50N – Ideal for watersports use including dinghy and keelboat sailing. 50N buoyancy aids should only be used in calm, sheltered waters where help is close at hand if required.

100N –  A sufficient buoyancy for children’s life jackets or for those in calm, sheltered waters.

150N – Typically used in coastal and inshore waters when sailing but can also be used for general offshore and rough weather use. If the user is not wearing heavy clothing, there is typically enough buoyancy to keep a man overboard’s face out of the water.

275N – Primarily used for offshore and/or commercial use where heavy clothing is worn. The extra buoyancy provided will ensure that the advanced features of the life jacket will work to their full potential, keeping the man overboard as safe as they can possibly be in the water.

If you have looked through our excellent range of life jackets you will notice that there is a wider range of buoyancy levels than mentioned above.

This is because the four buoyancy levels mentioned above are the industry standard. All our life jackets are from industry leading brands who aim to exceed safety standards, hence the reason why there is a vaster range of buoyancy levels.

This doesn’t necessarily mean a 170N Life Jacket is better than a 165N Life Jacket because it has more buoyancy, all life jackets contain different features that are more suited to certain individuals. Below are some features we think are worth looking out for.


One of our most frequently asked questions is 'I am this height/weight, will this life jacket fit me?'. The short answer is, yes. 

Most life jackets are fully adjustable, ensuring they can cater for all heights which is why there are no size options. However, in some cases, like with Spinlock's Deckvest 5D, there are different size options in order to ensure a precise fit. 

A life jacket will not fit a certain person just because of their weight. If you are heavier, or are wearing heavier clothing, you may want to opt for a higher level of buoyancy, ensuring if you do go overboard, your airways are kept high above the water.


As mentioned, all of our life jackets have their own special features and accessories – certain features will suit certain individuals more than others, here are four features we recommend looking out for.

Crotch Strap:Life Jacket Harness & Crotch Strap
Life jackets typically have one or two crotch straps, these will prevent the life jacket from slipping over your head. Crotch straps are strongly recommended by the RNLI.

Spinlock Deckware Pro HarnessHarness:
A harness will provide a secure tether point to your life jacket, allowing you to use a strap to attach a secure point - preventing a man overboard situation. We sell a fantastic range of harnesses from industry leading brands.

Seago Automatic Life Jacket Light

Life Jacket Light:
Although not commercially approved, a flashing/strobe life jacket light will make you significantly more visible at night or in poor visibility, making it a must-have accessory. Just like harnesses, they feature on a lot of life jackets and can easily be retrofitted. Check out our great range here. We recommend Spinlock's DAME Award Winning Life Jacket Light (Click here).

Spinlock Deckvest VITO SprayhoodSpray Hood:
A spray hood will keep spray and water blown in your direction away from your airways, significantly reducing the risk of secondary drowning. Thanks to their luminous colour, they also act as a great detection aid as well as ensuring no heat escapes from your head.

You can see our full range of life jacket accessories here.



Advanced Features:

As we only stock the best life jackets from industry leading brands, the life jackets we sell often contain advanced technology that is unique to each respective brand. Here are four special features (one from each brand) that are worthy of your attention.

Crewsaver Life Jackets – Halo Hood System:
Crewsaver’s ErgoFit+ Life Jackets feature an innovated Sprayhood system. This system works with the shape of the inflated bladder to significantly reduce the risk of water inhalation and heat loss. The spray hood contains an internal panel that offers further protection against spray and doubles up as an anti-glare panel, protecting the eyes of the wearer.

Seago Life Jackets – S Design Lung Technology:
Seago’s S Design Lung Technology is a common feature on their excellent range of life jackets. This technology guides water away from the mouth and head, increasing splash defence and in the process preventing the risk of secondary drowning.

Spinlock Life Jackets – Harness Release System:
The latest innovation from the Queens Award winning brand. Spinlock’s Harness Release System ensures that a simple release from a safety line is easily accessible with either hand, even when fully loaded. This significantly reduces the risk of an accidental snag or release. You can find this system on Spinlock's Deckvest VITO Life Jacket.

Childrens Life Jackets:

The RNLI emphasize that you should only purchase a life jacket that fits your child, not one that they will grow into as this may result in the child slipping out of the life jacket or the life jacket floating high in the water, leaving the child’s mouth and nose submerged. The RNLI also advise that it should not be possible to lift the life jacket more than 2.5cm from the child’s shoulders.

Childrens life jackets have different sizes for different weights, so before making a purchase ensure that you weigh your child.

Pet Life Jackets:

We could not forget our furry friends! Pet buoyancy aids should fit nice and snug so the animal cannot twist or turn out of it. A lifting handle should also be easily accessible. We sell a Crewsaver Pet Float that is perfect for any trips out onto the water with your pets.

Frequently Asked Questions:

What is the difference between a life jacket and a buoyancy aid?
Once activated, a life jacket is designed to keep your airways clear of water, even if you are unconcious. After the life jacket is activated, you'll need to repack it and purchase a replacement re-arming kit.

Buoyancy aids are simply designed to aid you with buoyancy when you fall into the water. For watersports including kayaking, windsurfing and dinghy sailing, we'd recommend a buoyancy aid over a life jacket.

Some of your life jackets have a harness option, what is this?
The harness variation of a life jacket contains a d-ring that provides you with a secure tether point - you can then use a strap to attach to a secure point.

Sources of information:


If you have any further questions, our highly experienced crew members will be more than happy to assist  - give us a call on 01634 295 233 or send an email to [email protected].


Posted on 2021-04-25 13:04:01
its really all about the weight of a person's head, the more out the water the better

the 50N is equivalent to raising a 5kg weight above the water line assuming the rest of a persons body is at the same density as the water its in, in fact the average body is at an average density of circa 970mg/m cubed, average water density is never less than 1000mg/m cubed up to 1020 in salt water, so a little bit to play with

the average weight of a persons head is 5kg, so a 50N vest is designed to get the average head fully out the water, assuming your haven't got lead ingots in your pockets, or cement wellingtons
Peter howell
Posted on 2021-04-11 00:11:27
This information has been very helpful in making the decision of which are the most practical life jackets for my family use.
Jet Pilot
Posted on 2021-01-22 10:20:38
Thanks For sharing useful information
Posted on 2020-12-14 07:46:21
thanks alot for this blog alo informative thanksc for this
Posted on 2020-12-14 07:27:30
thank you so much!!! keep posting thank you

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