Review: Whites Thermal Fusion undersuit

The nemesis of every cold water diver is the cold water. Therefore, the quest of every cold water diver is to maintain some amount of body heat when diving, or at the very least make an effort. 

An arduous task, that is only possible though the use of a drysuit and an undersuit.

One of the newer undersuits available is the Whites Thermal Fusion. Is it the future of cold water diving?

We'll see.

TECHNICAL STUFF (what Whites say)

The Whites Thermal Fusion is made up of two layers. The first layer, a loose cut thermal core constructed of Polartec 200 fleece, fits a wide size range and does not restrict mobility. The second, outer layer, is a Polartec Power Stretch Procompression skin which streamlines the inner core to the divers body, provides a custom fit, and allows maximum range of motion.Sounds fab doesn't it?





Lets face it, undersuits look awful on the majority of divers. Very few of us are built to prance around in a tight fitting one piece affair. Even the latest trend of 'the onsie,' is (thankfully) confined to one's bedroom; or the streets of certain Belfast housing estates.

The Whites Thermal Fusion looks pretty damn good in the grand scheme of things. It's black, which is always pleasing, and has a nice matt look outer layer.The branding is minimal, consisting of 'Whites' around the neck, 'Fusion' text on the right shoulder, and a small logo centrally placed on the back.

Whites logo on back
Once donned, the suit looks pretty slick. Moreso on me.Quality wise, only time is the true indicator, but it certainly seems well constructed, and I still havent managed to break it yet.


The undersuit has the obligatory thumb and feet loops, to keep the arms and legs in place when donning the drysuit.
thumb loops
feet loops

A nice addition are the 2 pockets. Pockets are something that are often omitted from undersuits, I have no idea why; I never imagined a pocket was hard to make.

The Whites Thermal has a pocket either side of the suit which meet in the middle, sitting nicely around the belly area; kinda like pockets on a hoodie.

front "hoodie" pocket

Whites have also included the Air Transfer System, or ATS if you're into those wee acronym thingies. The science is impressive I'm sure, to me it's just the combination of 2 vents. A vent on the chest allows air injected into the dry suit to enter the undersuit, and a vent on the shoulder allowing air to be expelled through the dry suit dump valve.

chest vent

shoulder vent

Another worthy mention is the convenience zip, just like on a pair of jeans. This not only enables a bloke to take a pee without doffing the suit, but allows all divers to route a pee valve without cutting a hole in a nice, new suit.

convenience zip


conditions: the suit was worn next to the skin, under a membrane drysuit, in sea water, fourth element arctic socks, temperature of 6C / 42F, duration 60 minutes, average depth 17m.

Donning the undersuit

Donning the suit was a bit weird. The entry zip runs from should to shoulder, dropping down across the chest. Once opened the diver steps into the suit, pulls the flap over the head and zips closed. The only area that proved irritating was the legs. The 2 layer system gets a little bunched up around the calves until fully donned. There is a definite technique, but after a few goes it becomes bearable.

Zipped up, the outer layer did exactly as designed and compressed the inner layer close to the skin, resulting in a lovely tight, snug fit. The suit was very comfortable, creating immediate warmth, and despite being tight to the body was not restrictive. Even with exagerrated movement of arms and legs the suit returns to a nice state of equilibrium.

Once on, popping one's hands into the pockets is strangely comforting.

Donnning the drysuit

Due to the close fit of the Whites Thermal Fusion donning the drysuit was an almost enjoyable experience. The one piece didn't move an inch, the arm and foot loops worked perfectly. The test dive was conducted from the shore, which involved a reasonable trek down to the site, and a bit of standing around. Even layered up with hood and drygloves the overall feel was still comfortable; no crazed sweating.

Diving the whites thermal fusion

In water the first noticeable aspect of the undersuit was the mobility. The stretch material worked superbly, allowing full range of movement; even throughout a pesky twinset valve drill. The mobility was unlike any other undersuit system previously expereienced. It was very impressive.

The water was cold, no doubt, my face told me as soon as it hit the water. After several minutes in the water and adding only enough air to the suit to remove the squeeze the dive commenced.

First impressions were excellent. I could feel the water pressing against my body, which I wasn't expecting, as my usual layering system is so thick I don't feel anything physical; but I wasn't cold.
There were no weird bouyancy changes either. My trim felt normal and I didn't need any additional weight.

30 mins into the dive my hands began to get cold. The extremities always get cold first, as the body draws all the heat to the core in order to sustain vital organs. By 40 mins I was ready to leave the wreck and swim for shore. My feet were also getting cold, but my core was still warm and there was no shivering.

At the safety stop, dive time of 50 mins, I began to feel the cold all over. A little flailing of arms and legs generated a bit of heat which allowed the remaining 10 minutes to pass by without unbearable distress. It appeared whatever heat movement generated was maintained well by the undersuit.

At the climax of the dive I was feeling the cold, but not shivering; I wouldn't have wanted to extend my bottom time; I hate being cold on a dive, i don't do shivering, and 60 mins was my limit.

It also insulates when wet. On a later dive I had a neck seal failure and the undersuit became very wet down the front. I hadn't realised until post dive. The suit was wet on the outside, but the fleece lining against the skin was dry.


The Whites Thermal Fusion is an excellent undersuit choice for cold water divers, and I imagine worn under a neoprene suit it would be perfect, even in extremely cold water. The thermal properties are very good, but the best thing about the suit is the mobility and comfort; it is simply outstanding.

It is not warm enough worn alone for long dives, or extended decompression, certainly in waters below 6C. On subsequent dives I added fourth element xerotherms as a base layer, which worked very well for increased duration. With that system I completed 3 dives in one day in a 5C freshwater quarry no problem, and outlasted my buddy!

The only downside with the suit is the lower calf region. The double layer system ends around that area, and a stretchy section continues to the feet and feet loops. 

Without long socks the lower calf would only have single layer insulation. I don't quite understand why the suit doesn't continue to the ankles; perhaps Whites just know everyone owns fourth element arctic socks?

PROS: Comfortable, warm, superb mobility, stretchy to facilitate extra layering, has pockets.

CONS: Technique in donning, requires good long under socks. Expensive.


  1. Excellent write-up, thanks. I've been considering one of these for some time, but have always been put off by the cost... Think you've made the decision for me :-)

    Keep up the good work, I do enjoy reading your diving adventures!

  2. Thanks Ian - i'm glad the review was of help to you! :D

    Safe diving, and keep coming back; there wil always be plenty of diving adventures to be had!

  3. Thanks for the review - turns out I just ordered one...glad you're review supported the decision ;-)

  4. Excellent James!

    Post back and let me know how you get on. It would be interesting to get your take on the suit also.

    Safe, warm, diving!

  5. Thanks so much for the detailed review, I am thinking of purchasing a new set of undergarments and wanted to do some internet review searching first (need more warmth and good mobility). As I do own a neoprene suit, this may be the perfect solution for me. Being a lady, I do get chilled easily. However, since I live in Canada, I have a local shop that rents these undergarments, so I can try before I buy. Thanks again for taking the time to post a review for everyone! :)


Thanks for commenting, I appreciate it!

Safe diving buddy.