First off you don’t have to be a technical diver to dive GUE/DIR. It’s a swell system that will help divers of all levels.
For this style of diving the basic requirements are: a well fitted drysuit that will not compress with depth (e.g. not uncompressed neoprene).
I dive a CF200 - all crushed neoprene. It is pretty sweet underwater but I'm not a huge fan of the thickness of the material. It is trickier to don and significantly heavier when wet than a shell suit. It is a warmer suit than a trilaminate (TLS/FLX extreme/CLX/etc) and DUI estimates through it’s internal testing that the difference is about the same as the improvement from adding a fleece vest (approximately 5 degrees F). Some people notice a bigger difference, but it can be hard to judge because the suit takes much longer to initially cool off and is deceptively warm at the beginning of the dive. If you decide to go with a CF, realize the exhaust vent placement is wonky and try to get them to place it a bit further back, it’s normal position is trickier to vent than it needs to be.
As for the 50/50, the biggest advantage would likely be from wear resistance and not warmth. If you’re adding 5 degrees with a full CF suit, you’re only adding 2.5 degrees with a 50/50, which is very, very little. However, if you're going to be doing a lot of crawling over rocks, the 50/50 may be a better choice because of the added durability in the legs. Also, CF material is a bit stretchy and you’ll probably get a slightly better fit in the legs than with a trilam. Any neoprene suit will take a long time to dry (a day or two) and will stay heavy when wet. If you plan to travel, this is a serious consideration because of flying weight – so consider this when choosing.
Just in case you’re considering a back-entry suit, I would recommend against it. The back zipper can interfere with flexibility, but more importantly back-entry suits don’t usually come with extendable torsos, which are very important when it comes to valve manipulations (especially in single tanks).
Cave cut is not necessary except in the very specific applications it was designed for. You’re probably not planning on doing six hour scooter runs in 300 foot deep caves too soon, and when you do you’ll probably have a suit or two dedicated to it. I would recommend against cave cut - you will lose flexibility if the suit’s cut is not perfect, the suit will be harder to don and will likely leak more.
Many of the TLS suits I've encountered have some troubles with leaks. The material is not very resilient. I would encourage you to look at the FLX extreme - a slightly more durable laminate suit that won't be as prone to pinholes but will retain a high degree of flexibility.
Zipseals are kosher. Make sure your head fits through the zip ring neck, as larger heads won't be able to squeeze through. A larger ring is on the way but is not yet available. Zipseals on your wrists are especially nice for cold water because you can attach drygloves, which will improve your overall body temperature even if your hands don't get cold. Cold hands act like radiators because of the high blood flow. There are other options for drygloves, but they typically require rings that can interfere with valve manipulation. Ring systems will allow you to don your gloves after your suit though, so they’re something to consider separately, they have advantages and disadvantages.
Whatever you do, get pockets - big pockets – as big as you can find. The stock large bellows pockets are nice, but large Halcyon explorer pockets are the best I’ve seen. Larger pockets have few downsides and with thick gloves it can really be a trick to get into a smaller pocket. Ideally, you want the pockets a little higher than DUI typically puts them – around 1-1.5” up will make them much easier to get into. GUE/DIR generally favors Velcro pockets because they fail open and are a bit easier to get into. Admittedly, Halcyon’s pockets have an inexplicable zipper mini-pocket on them, but hey, nobody’s perfect.
DUI will stitch and glue the pockets to your suit. This makes for a much sturdier base and limits their tendency to peel off (as glue-only pockets tend to do). Of all the things you can get fitted at the factory, this is probably one of the most important. I would say the most important addition is kneepads, only because as far as I know, they can’t be fitted after the suit is made. If you want kneepads, and you do, get them on your suit when you order it. A cloverleaf is nice too, it protects one of the highest wear areas of the suit and works especially well as a nad pad for scootering.
Another delightful addition is a P-valve that is used with external condom catheters for guys or a she-p for gals. They are worth every penny/bit of sensitive skin that they’ll cost you. You can order the valve fitted from the factory or save some money and do it yourself (installation does involve punching hole in your suit though). DUI fits the Halcyon one and I’m a big fan of this particular valve, but I have admittedly never tried another. If you decide to shop around for other choices do your research, some very unpleasant things can happen when P-valves fail. Also, when you do decide to get one, find a syringe that will fit the tubing and wash the tube and valve after every use with alcohol or a bleach solution – urinary tract infections are no fun.
I really can’t stress how important a P-valve is. You want one. Get it.
As for footwear, I’m a big fan of turbosoles. This is largely a preference thing, and will depend on your state of wellbeing and preference. Turbosoles allow more ankle flexibility in the water and arguably a bit more finesse. I find them far more comfortable. However, if you have injured your ankles in the past or a have a trek to your divesite (in gear) then rockboots may be the way to go. Either way, it’s not too expensive of a retrofit should you feel the need down the road to switch, so don’t stress out about it too much.
One option for turbosoles is the “mexico mod” that adds some extra material in high-wear areas on the sock. It consists of three parts – toe reinforcement, heel reinforcement and a strip of material around the ankle. The toe and heel reinforcement have basically no downside, but the ankle makes it a bit of a hassle to get the turbosoles on. If you decide the cost is worth it for the durability increase try to get them to do the toe and heel without the ankle. These two areas are the highest wear and reinforcement is a good thing. Again, this is a fairly minor bit and it’s not too big of a deal either way.
If you have a buddy that like filming or you just like looking good, I encourage you to get an overlay that goes all the way down your arms in a color that’s not black. It will make you look better on camera – personally, I like blue, but you’re allowed to have your own favorite color. Red contrasts well with blue/green water (colors that look good together are opposite on a
color wheel). The wheel suggests that pink would contrast well with green water, but nobody’s been brave enough to try it on a suit yet.
Undersuit selection is actually one of the more important bits of choosing a drysuit, especially a shell suit (like all of those I’ve discussed here). Though the suit keeps you dry (when it’s working) the undersuit is what keeps you warm, and that’s really all a drysuit is supposed to do. For cold water diving, you’re going to end up in a 400 gram undergarment like the DUI XM450 or the Santi Extreme 400 if you’re doing anything but sub-hour dives. Personally, I went with a 300 gram to start (the powerstretch 300 or the fourth element arctic are examples) which is nice because they’re quite flexible and when you’re a newer diver it will keep you plenty warm. Thinner undergarments also tend to be easier to learn to dive a drysuit on because they’re a bit easier to vent. I would encourage you to start with a similar undergarment and upgrade as you see fit. Undergarments will crush as you use them and despite their high cost are a “disposable” product that will have to be replaced; you’ll have to get two anyways, so start with a trainer rather than jumping straight to the big leagues and trying to save some money.
For GUE/DIR diving, you’ll want to stay away from suits that rely heavily on loft for warmth. These are easy to recognize because they’re poofy and big, like a mountaineering jacket. Typically for GUE/DIR, you will dive a suit with a minimum amount of gas in it, which won’t allow a poofy undersuit enough gas to fully “loft” and warm up. If you do get an undersuit like this and you dive it underlofted, you’ll be cold, which is sad because you spent three grand to be warm. Thinsulate or polarfleece only needs a little bit of air to insulate fully, so they’re the choice materials. All the undersuits I’ve named are made from kosher materials, so they’re a good place to start.
Other additions to increase your thermal comfort include heating vests and nice thermal base layers like bodyzor from waterproof. Both of these will significantly improve your comfort, especially if you’ve been diving your undersuit for a while and it’s a bit more “well loved” than it should be. Lamont has a stellar post on this, but his blog’s down, so hopefully he’ll get off his unemployed ass and fix that (please don’t ban me). Thermal concerns around here are similar to those in your neck of the woods, so it's will be a good read if it comes back up.
Ultimately, your choice of undergarments will depend on your personal tolerance to cold. Note that your tolerance to cold will go down as you dive more (longer dives, less movement – trust me on this one).
DUI hoods suck. Get a warmer 7mm or 10mm hood from (Waterproof and Fourth Element make good ones) or buy the mother of all hoods – the Otter Bay 12mm neoprene helmet. Not only will it keep you warm, but it can also probably protect you from small arms fire. They have an ugly logo, but they’re custom made and quite toasty.
The absolute best thing to do is to attend a DUI Dog Days rally and try suits out for yourself. There's one May 14-15 in Gloucester, MA (you can see all of them
here). You get try suits out in the water, get measured by a pro for your suit, see if you fit stock suits/undergarments and generally have a blast.
Common alternatives to DUI suits include the Whites Fusion (a favorite of local board junkie TS&M), Diving Concepts suits and Santi Suits (a favorite of many in these parts). Though I’m a big fan of DUI suits, any drysuit is a big investment and it would benefit you, even if only for comparison’s sake, to check out some of the competitors.
Sorry that got kind of out of hand.
