Look at them, look at how stupid they look. The greatest technology the world has ever seen, and these Westerners use it to make themselves look like cats and to fuck robots.
Rusalka- The Marine Folk
The Neo-Soviet Empire at the heart of the Eurasian Alliance knew it was in no position to contest the economic or technological might of the Atlantic Federation in space. Instead of wasting untold amounts of money and resources playing chase, the Alliance decided that it was going to go the conservative path and stick to what it was good at, and where it's strengths were. For the Neo-Soviets that meant tanks, heroic power armor troopers, submarines, and potent aerospace fighters. (It is a point of consternation to the Federation that despite their tech advantage, their front line fighters like the Corsair III are on par with their Alliance counterparts, and in some instances, inferior).
The Eurasian Alliance has been well acquainted with the nuances of genetic modification as well as the creation of phenoclades. The most successful of the Neo-Soviet 'clades have been the Morskoi Ilyudi, or the Rusalka. The Rusalka have been genetically engineered and tuned to live in Earth's predominant environment, the ocean.
The Rusalka have a variable metabolism and can lower their pulse, respiration, and body temperature for prolonged periods of time, making life support for them much easier. They also have denser muscle tissue, a layer of subcutaneous fat, and thicker almost scale like skin giving them protection from the pressure of living underwater. A rusalka can free dive up to 200 meters (6 atmospheres) without ill effect. The most important modification is that a rusalkan can switch from breathing air to breathing water. The transition takes about a minute either way, but going to water breathing requires switching over to the low energy metabolism.
The Neo-Soviet submariners, residents of the morepolozhinye cities, and seacology residents have high percentages of rusalkans. The ability to survive underwater without SCUBA gear or other equipment generates a laid back attitude among the rusalka. This tied with their variable metabolisms make them seem lazy, but rather they are much more deliberate than surface dwellers.
Drawbacks and Restrictions
Rusalkans typically avoid cybernetics and cyberware whenever possible. Something about bionics and salt water not getting along. They are also stoic to a fault. While they are hard to frighten, they are equally hard to motivate. Narcotics and drugs typically have a stronger effect on rusalkans because of their altered metabolism, suffer double the normal effect.
Rusalkans, due to the level of biomodification, are not cross-fertile with non-rusalkan humans.
The Atlantic Federation and the other world powers know about the Rusalka, but not the extent of their numbers. The other nations recognize that the Neo-Soviets are decades ahead of them on engineering aquatic biomods, but for the most part they consider it a dead end and think the Alliance foolish for wasting resources like it has on the program. The ACPS is more concerned, as it shares terrestrial and aquatic borders with the Alliance. The Chinese have even more so underestimated the Rusalkans and consider them freaks rather than a genuine threat.
Captain Valery Sablin of the submarine cruiser Storozhevoy has made a name for himself hunting pirates off of the Kamchatkan peninsula. His crew is entirely rusalkan, and because of this, his ship can go quiet and dark much longer than a normal human crewed sub can. Sablin's patience and cunning has earned him a reputation among non-Alliance naval personnel as the 'Patient Shark' as he has ghosted Federation ships, Coalition ships including a Nipponese security frigate, and sunk over two dozen pirate and rogue ships, including a pair of EUdAS attack submarines operating in Alliance waters.
Codename: Siren - Siren is an Alliance saboteur and espionage agent. Her Rusalkan heritage is concealed by regular dose stimulants and cosmetic surgery. Aside from being a highly trained Neo-Soviet agent, and an aquatic humanoid, she is also a gifted parapsychic with abilities that allow her to emotionally manipulate people. Her MO is to lure targets aware from security personnel and to a body of water. Her victims almost always die of drowning.
Additional Ideas (1)
An much more extreme modification, the Morzh mod demonstrates the extent to which the Neo-Soviets have mastered genertic engineering. The morzh phenoclade from the waist up is predominantly human, even if the features are blunt and crude looking. From the waist down, the morzh has more in common with marine mammals than with humans. The legs are fused together into a tail, and the feet are spread out into a tail fin, giving them strength and control moving around underwater. Unlike the rusalka, the morzh mod is designed for deep sea operations, and spending extended amounts of time underwater. Where the Rusalka cannot go much further than 200 meters, a morzh can free dive as deep as 1000 meters, and can do so in freezing temperature water.
There are several hundred Eurasian morzh, but they are all located in arctic seacologies or deep sea operations. In these locations they operate and inspect underwater listening and snooping equipment, spy on ACPS and Coalition underwater facilities, and salvage/loot underwater wrecks.