Life jackets and buoyancy aids: How to choose one

Buying a life jacket that’s on offer without looking at its specs just to keep it on board in case of emergency is not a good idea. It’s worth choosing the model carefully and making sure it fits well, so that it can fulfil its purpose - keeping you alive in case you fall overboard. 

The type of life jacket or buoyancy aid you need strictly depends on what type of sailing you plan to do. Some models are made for use in sheltered waters, some for coastal sailing, and some for offshore passages. Their weight and bulk varies dramatically. Due to a person's natural buoyancy, the weight of the wearer is not usually a deciding factor when choosing a lifejacket. 

Let’s look at the different types of life jackets and buoyancy aids available in the UK and where they should be used. These are often referred to as personal flotation devices (PFDs) and are rated based on buoyancy in Newtons. 10 Newtons equals 1kg of buoyancy.

Life Jacket vs Buoyancy Aid

Whilst both help you float, they are suited to quite different situations and are not generally all that interchangeable. 

Buoyancy Aids 

Generally foam jackets that are covered in a tough material and worn for water sports such as dinghy sailing, paddleboarding or kayaking. They are designed to be as low-profile as possible and assist you to float when in the water. Other than wearing the buoyancy aid, you don't need to do anything to make it work. They are usually rated at 50N.

Life Jackets

Life Jackets are designed to keep the wearer afloat and in many cases, the head correctly positioned when in the water. They can be the old-fashioned and bulky foam style but, in most cases, are either automatic or manually inflating chambers that are slim and ergonomic, as until required, they are deflated. A lifejacket should be worn for anyone coastal or offshore sailing, working on moving water or in commercial operations.

Life Jacket Types At A Glance 

We have summarised all this information in the table below, so you can refer back to it while choosing your lifejacket.

*165N, 170N, 180N & 190N lifejackets remain certified as 150N and carry additional buoyancy added by the manufacturer. Their official rating will remain 150N.

Foam filled 

These 50N buoyancy aids and 100N lifejackets are filled with foam and, although lightweight, can be bulky in the larger sizes but require less maintenance and can be used over and over again without needing to be re-armed - useful when learning to sail a dinghy. 

50N 

A 50N buoyancy aid has a minimum of 5kg buoyancy. These are to be used by confident swimmers who are engaged in water activities near the shore such as kayaking, paddleboarding or dinghy sailing or for those doing watersports where help is close at hand. The person wearing it needs to be able to swim in order to get to safety - hence this is a buoyancy aid, not a lifejacket. It is not designed to turn the wearer face up if they are unconscious. 

100N 

These provide a minimum of 10kg of buoyancy, which is suitable for calm, sheltered waters. They do help the person float, but may not have sufficient buoyancy if the user is not able to help themselves. It also may not turn them from a face-down position. 

Gas Inflated 

The following 150N and above lifejackets have the buoyancy provided by CO2 gas. This is stored compressed in a small cylinder fitted inside the lifejacket. If the wearer falls into the water, the gas is released (either manually or automatically), quickly inflating the lifejacket to its full size. Once recovered from the water, the lifejacket has to be deflated, re-armed with a new gas cylinder and water sensor and then re-packed before it can be used again. We recommend automatically inflated lifejackets as they will inflate even if the wearer is unconscious when they enter the water. 

There are two types of automatic triggers for lifejackets: water-sensitive or hydrostatic. Water sensitive is triggered by contact with water, whilst hydrostatic triggers under a certain amount of pressure. The hydrostatic trigger requires immersion in water to trigger rather than just being wet, which leads to less chance of an accidental firing of the system.

150N 

A 150N lifejacket offers 15kg of buoyancy. This type of device can turn the person in the water into a safe position to reduce the risk of drowning. It can be used in coastal and offshore. However, their buoyancy capacity is still rather limited - if you wear waterproofs and/or heavy clothes, their efficacy is diminished. Do you sail with waterproofs and lots of layers on? You may want to consider upgrading. 

165N and 170N 

These are the most commonly seen lifejackets on yachts, powerboats and ribs in the coastal waters of the UK. If you can expect some rough weather every now and then in your area or if you wear layered clothing and waterproofs, it’s wise to get a 165N or a 170N PFD, which provide respectively 16.5kg and 17kg of buoyancy. These tend to be compact, yet well-buoyant. Coastal sailors who go out often choose either model. Many racers buy them because they keep you afloat without being very bulky, allowing them to move around on deck easily. 

180N and 190N 

Are you going offshore or on long passages at night or in colder climes? You’ll probably need a lifejacket with 18 or 19kg of buoyancy. The 190N models are bulkier sets of kit, but they will keep you safe even in heavy conditions - when swimming isn’t possible - until help arrives. 

275N 

Providing 27.5kg of buoyancy and will turn you face-up even when you have heavy clothes on. It’s the lifejacket of choice for people who work on fishing boats and commercial ships and some offshore yacht crews. These are not usually available off the shelf at chandleries but are readily available to order.

Tips for choosing a buoyancy aid or life jacket 

For dinghy racing, most sailors opt for a 50N buoyancy aid. 100N ones are more suitable for less confident swimmers or for use on larger cruising dinghies. 

If you’re a coastal racer or sailor, or for motor boating, a 165N lifejacket is usually enough. For offshore racing or cruising in poor weather, you’ll want a 170N or a 180N, so you can avoid some bulk. Offshore racers or cruisers who go on multi-day passages or longer should buy a 180 or 190N.

If you just want to own one lifejacket, get one that’s suitable in heavier conditions, so when you are realistically at risk, you can trust it. The extra bulk will be worth it.

 If instead you’re open to investing in more than one PFD, you could opt for a combination of a 165N for sailing and racing in coastal waters and a 180N or 190N for longer, offshore trips. 

How you intend to use your lifejacket is key to choosing the right one for you. Bear in mind that the forecast isn’t 100% accurate, so the wind could be stronger than predicted some days. 

As for sizing, lifejackets come in two sizes: adults and junior. Junior ones are for kids weighing up to 40kg, while adult ones are for people over 40kg. This is because all adults have a 5kg net weight when floating in the water. 50N (buoyancy aids) and 100N (usually foam lifejackets) models come in different sizes - they go from baby to adult XXXL. 

In all cases you’ll need to check weights and sizing carefully and take measurements before ordering. Good lifejacket brands include Crewsaver and Spinlock. Remember: a lifejacket can save your life, so don’t skimp on such an important piece of safety gear. Buy the appropriate model and size and service it regularly. Wear it at all times underway, or at least as soon as you notice the wind picking up or at night. You may never fall in the water, but if you do, you’ll be thankful your lifejacket works and keeps you afloat with minimal effort. If you’re unconscious, a good lifejacket will turn you so your face can stay out of the water until help arrives.

Life Jacket Accessories and features to look for 

Harness and Safety lines 

The preferable option to becoming a ‘Man Overboard’ (MOB) is to stay on the vessel and, failing that, at least stay attached to the boat. A harness with a safety line clipped to a jackstay or other strong point is designed to stop you from drifting away from the boat in the event of a slip or trip. This makes it easier for the crew to get you back on board quickly. If you can use a short safety line, then you may avoid falling in altogether - a much better option! Clipping on to the boat is advisable if you sail alone or at night or in poor conditions. Most 150N and above lifejackets have the option of an integral harness. 

Lights 

A must for anyone who sails at night. A person is difficult to spot in the water at the best of times, but at night they are practically invisible. The life jacket light is installed inside the life jacket and automatically activates when the life jacket inflates on contact with the water. It emits a very bright flashing white light, making spotting the MOB much more likely. The 180N and above life jackets often have these pre-installed. 

Spray Hoods 

If you sail offshore, on longer coastal passages or in rough weather, it’s recommended to fit your lifejacket with a spray hood - it makes you more visible and reduces the amount of spray you inhale. You can keep your spray hood stowed in the lifejacket or neatly folded up in your waist belt, so that you can deploy it quickly when conditions worsen. 190N and above lifejackets are often supplied with these fitted. 

AIS Beacons and PLBs 

These electronic devices are the ultimate aid to getting found and recovered from the water quickly. Some can be fitted into the life jacket and automatically activate when the life jacket inflates; others are worn on the life jacket harness in a pouch and are manually activated. 

Spare Re-arming Kits 

Always keep spare re-arming kits aboard your boat; that way you can re-arm a lifejacket for use immediately. There are many types of re-arming kits; make sure that yours are the correct ones for your lifejackets.