dry suit thermals or semi dry wetsuit

[arcticat99]

hi just recently received my open water certification up here in Canada last week and yes the water in the fall is getting pretty cold .for my open water i rented a 7 mm john with 7mm jacket .14 mm at the core.first question will a 1 piece semi dry wetsuit be warmer than the previous i rented second if i were to buy a dry suit is there a big difference in the thermal underwear you buy at a dive shop compared to thermals you can purchase for snowmobiling other than a "bare "name and a few hundred dollars more

 

[KevinNM]

A dry suit that is properly fitted and with the right undergarments will be a lot warmer than a wet suit.

You dry suit gets fully saturated with humidity, so you need to avoid cotton and another fabrics that don't keep you warm when damp. You want some sort of wicking base layer against your skin and the heavier mid-layer on top of that. I typically have a sheen of moisture on the outer surface of the mid-layer where it touches the actual drysuit when I take the dry suit off just from my sweating in the suit.

One thing about dry suits is that they will eventually leak. A not quite closed zipper, a fold in a seal, or leaking valve, lots of things. The drysuit-specific mid-layers are generally decent at keeping you from freezing when they slowly flood. At least when I've had it happen. I haven't had it happen in really cold water (and large-scale flooding you will know about fast), but I've sometimes noticed slow leaks when I'm getting out of the water and felt the squishing walking out of the water.

 

[chrisch]

It's very hard to beat a good drysuit. Once out the water you can avoid all the discomfort of getting out a wetsuit and drying off. If you dive cold water it is the best thing to spend your money on - buy one rather than any other equipment. You can rent good regulators but a drysuit is personal to the diver that wears it.

Undersuits are important, but much less so. Be careful of garments that might "fluff" and block the drysuit valves and avoid things that rely on "lofting" as the depth will squeeze the insulation out of them (I guess a lot of snow-related garments fit that category). With a membrane type drysuit you can use layering to good effect. A neoprene drysuit gives quite a bit of thermal protection in it's own right and needs much less under it to keep warm.

Kevin is right that sweat and general humidity are issues and again the better garments will give the best results. Personally I find that it is the out-of-water activities like carrying kit to the boat that are the most problematic for this issue. I can do an hour underwater and not really notice any difference in moisture at all.

I have dived lakes in 3C water and had a pleasant dive. Without a drysuit such a dive is impossible. To my mind that makes the cost of the drysuit well worth while. If you look after it and store it properly they last 10 years or so, more often. It is a lot of money to spend but if you live near good cold water diving it is worth it.

 

[RyanT]

I'm really comfortable in my 7mm semi-dry suit in water down to about 55 degrees and for dives that are 45 minutes or less. If I were going to regularly dive water much colder than that, I would go dry.

 

[high/baric]

About your other question. The important things when it comes to wet suit insulation are fit and thickness. Even a "semi dry" wetsuit will allow some water to enter. As long as your wet suit fits well the water inside won't change too easily and will stay warm. A thicker suit will retain more insulation at depth, but also requires more compensation with BCD.

 

[arcticat99]

thanks for the replies .most oif my plans are to go tropics once every 2 years and just use my 3 mm shorty but in the inbetween times do some diving up north mostly in the summer with water temps mid 55f and up on my open water dive half the group(advanced) and up were in drysuits the rest were wetsuits and in the water it was fine it was between dives on the surface that it felt chilly .so the big question would be will i get my moneys worth out of a drysuit because on top of the suit you need thermals and take a drysuit course or just go with a semidry ,decisions decisions ,thanks

 

[Marie13]

I'd do with a drysuit. You'll be much more comfortable diving and for surface intervals. It extends your season, too. I went dry because I'm in the Midwest and the Great Lakes are better done dry.

 

[RyanT]

To expand on what high/baric said: the semi-dry term is actually a misnomer. A semi-dry is just a really good wetsuit. They limit water exchange better than a standard suit, making them a little warmer, but at the end of the day, it is a wetsuit. If you are planning to make some deep dives (greater than 100 feet) and especially deco dives that would require more time in the water, you might find that even a good semi-dry suit to be too cold. You'll get compression of the suit at depth and that reduces its insulating ability. Relatively shallow and shorter dives in the 55-60 degree range will be well-serve by a semi-dry wetsuit for most folks, otherwise go dry.

 

[chrisch]

.....so the big question would be will i get my moneys worth out of a drysuit because on top of the suit you need thermals and take a drysuit course or just go with a semidry ,decisions decisions ,thanks

You can often buy a decent secondhand drysuit and the undersuit need not be expensive at all. With a good crushed neoprene suit you don't really need much underneath and probably have all you need already. It will keep you warm in the water and on the surface interval. It will allow you to dive in the colder part of the year, often when the vis is better, the boat less crowded and last minute deals are available. If you intend to buy (rather than rent) a semi you need to look only at the extra cost, not the overall cost.

The need for a drysuit course is also debatable. The PADI one teaches you to use the suit for buoyancy and this is a bad idea so I certainly wouldn't waste the money on that. If you know someone that can teach you the basics without the cost that is worth a look at. There are a few techniques you need to get right but without knowing more about your circumstances it's hard to say what the best option is. If you do feel the need for a course you might get the store to include it in the drysuit price. I got a free (PADI) course with my first ever drysuit and as I was new to diving at the time it was a good thing and more in water time. I now understand the value of that was probably less than I thought at the time and certainly the course did not even touch on the issue of using the BCD - so I just learned the wrong technique which I needed to unlearn many years later.

 

[horsediver1]

Being a Northern MN diver I personally think you would be well suited to go dry. As water temps rise you cannot change the dynamics of a semi dry suit, with a quality drysuit you can add or reduce thermal ware thickness for the conditions. Drysuits do give you an additional 2-3 months of comfortable diving and if you get into ice diving just an added benefit of not having to undress damp in below freezing conditions. The key to a purchase is buy quality first and it will last if taken care of. My first suit lasted over 21 years before wear and tear of being a PSD took its toll from chemical spills wreck abrasions etc. Not to promote any product I use 4th Element under garment for 55 F. and colder and just a light poly propylene for warmer temps. Good to go no matter what the temps.
Just food for thought and opinion only. One more thing quality dry suit companies have over some products you will find they have multiple sizing so you can get an extremely close fit without the added expense of having to go custom sizing.