You bring up the point about the freediving suits that I was going to bring up next
Do they hold the thickness well with constant diving to deeper depths and staying there in contrast to free diving?
Why does it matter to the scuba diver to use a free diving mask?
A typical freedive suit is made from a jacket and pants. the inside is smooth rubber. This makes the suit slide on easier (when you use a lubricant) but it also reduces the exchange of water in and out of the suit.. so it is warmer.
The elimination of the additional nylon lining on the suit also enhances flexibility (which is more important on thicker suits).
The freedive suit has no zippers.. so no leakage
The freedive suit has an attached hood, so zero leakage around the neck.. You don't need to have a tight, constricting, uncomfortable neck seal at the junction of the hood and jacket, because there is no opening there to leak. The only water that can get into the hood is through the face seal and this is typically near zero.. in fact the smooth rubber seals so well you MUST let water into the hood initially or you will get an external ear squeeze.
The freedive suits are typically soft flexible neoprene, but it is not magic.. It compresses as do all other foam neoprene products.
What is important to understand is WHY a freediver would need a warmer, better suit. Typically, I think a 3 mm freedive suit is as warm as a 5 mm scuba suit - even when using a hood. When freedivers descend their chest crushes (a lot) and they lose a lot of buoyancy. Their suit compresses as well - just like a scuba diver. BUT scuba divers have a huge advantage, their chests don't crush AND they just press a button and offset (compensate for) the suit compression. Freedivers HATE this buoyancy swing!
Freedivers need to float at the surface, then FIGHT to descend against excess buoyancy and then when they pass a depth of maybe 30 feet or so, they reach neutral and after that, they just get heavier and heavier and begin to sink fast. So freedivers need to once again FIGHT buoyancy (this time negative buoyancy) to ascend AND they do this 20 or 50 times EVERY day.
As you can imagine, freedivers want to minimize this swing as much as possible.. So to do this they must have the thinnest suits possible. The thinner the suit the less the compression and this reduces the buoyancy swing and the easier it is to get down and up.
So hopefully you get a the picture why a freediver wants the thinnest and warmest suit they can get away with. Hoods are essential for providing thermal protection - with the least amount of rubber. So except for very warm water, hoods are pretty much always used and any kind of zipper is going to be avoided.
Also, i should mention that the freediver needs to really take large inhalations and the more restricted their belly and chest is, the harder it is to freedive.. so they demand a flexible, comfortable suit.
Freedivers want a small mask. As you approach a depth of around 80 or 90 feet, your chest is so crushed that it is impossible to get more air to equalize your ears. There are special techniques (not that I personally can do any of it).. but the point is that your air reserves for equalization become minimal even as you approach 60 feet. Every molecule of air you exhale into your mask on descent is air that can not be put to good use elsewhere. So there is a significant benefit to using a small - low volume mask.
Scuba divers have all the air in the world and mask equalization is not an issue. However, the latest generation of super low volume freedive masks are very comfortable, very easy to clear (and equalize) but some also provide EXCELLENT visibility. there is essential zero peripheral vision restriction - why? because the glass lens is so close to the eyes, that you can see up down and to the sides. It is sort like sunglasses..
The benefit of a very low volume mask to a scuba diver would be that it will not become an issue when dealing with strong currents, say when descending down an anchor line in a heavy current. With a big scuba mask, we hear about people saying they turned sideways and the current started to rip the mask off their face..
The benefit to scuba divers is less than for freedivers, but I have probably 20 masks in the garage and I use the same one for scuba and freediving.. there is no reason for me to switch masks when doing either activity.
Also.. a slightly leaky mask is a minor pain to a scuba diver.. For a freediver who is swimming face down in a vertical position , any water that leaks in is going to cover the entire inside of the face plate and destroy your ability to see, until you level off. This is a MAJOR pain in the butt, and you have no air to be putting into a mask to blow out water that leaked in because the air leaked out on descent... so once again,, a freedive mask MUST seal super well or it is not really functional.
