Hello everybody,   I have put together history and possible implementation of the German submarines in World of Warships.
Please keep in mind that this is just fan made, not official news of upcoming new ships.
Also I apologize for any grammar mistakes, english is not my native tongue.   I would love to see submarines in WoWs, but I also don't want to destroy this game.
If Wargaming wants to implement submarines in Random battles, then they need to do it carefully.
Also, I think that minelayer submarines won't make it into the game.   Please keep in mind, that submarine's characteristics (speed,...) are historically accurate 
and will be (most likely) changed. Reason is simple- speed of submarines is low and if they want to be
competitive, it should be changed. However, speeds of submarines, which are showed here, are good if you 
want to compare submarines from different tiers.   Adding submarines in game is only possible after the other issues in the current state of game are solved.   It is hard to say how would look submarine branch, if it make it into the game, because there isn't any other submarine branch 
to compare these submarines to.   If submarines would be implemented in game, I bet, that German tech tree would be the first that comes to mind.
Also, if submarines come to the game, all ships should be adapted (anti-submarine warfare...).   I think that submarines could have the same mechanics for reloading the torpedoes as in Halloween event.
However, the maximum depth, where can be submarine submerged, could be changed from tier to tier or by upgrading 
the hull of submarine. At the beginning, submarines could have only 2 different depth levels, where they can be submerged.
At higher tiers, for example Type VIIC or Type IX, they could have maybe 4 different depth levels.
If submarine runs out of air, she would be forced to the surface, where she begins to replenish her air supplies.   I start my tech tree at tier IV. Reason for that is simple. At tier IV, new players have a decent knowledge of game mechanics, so
if they meet submarines, they should be capable to counter them or know approximately how to react and they know their
ships quite well.   Main line:
Tier IV
Type II
Displacement: -surfaced: 254 t (Type IIA)
                                           279 t (Type IIB)
                         -submerged: 303 t (Type IIA)
                                                328 t (Type IIB)
Length: 40.90 m (Type IIA)
              42.70 m (Type IIB)
Beam: 4.081 m (both hulls)
Draught: 3.83 m (Type IIA)
               3.90 m (Type IIB)  Speed: -surfaced: 13 knots (Type IIA)
                                13 knots (Type IIB)
             -submerged: 6,9 knots (Type IIA)
                                    7 knots (Type IIB) Secondary armament: none (both hulls)
                   Torpedoes: -bow: 3 × 53.3 cm (21 in) torpedo tubes (both hulls) AA defence: Short range: none (Type IIA)
                                            1x20mm (Type IIB) Quick history:
The Type II U-boat was designed by Nazi Germany as a coastal U-boat, modeled after the CV-707 submarine,
which was designed by the Dutch dummy company NV Ingenieurskantoor voor Scheepsbouw den Haag (I.v.S)
(set up by Germany after World War I in order to maintain and develop German submarine technology and 
to circumvent the limitations set by the Treaty of Versailles) and built in 1933 by the Finnish Crichton-Vulcan 
shipyard in Turku, Finland. It was too small to undertake sustained operations far away from the home 
support facilities. Its primary role was found to be in the training schools, preparing new German 
naval officers for command. It appeared in four sub-types.   Notes:
I wanted something simple to begin this branch with. That's why I've chosen training coast submarine from WWII,
instead of WW I submarine.   In World of Warships:
There would be 2 hulls: Type II A and Type II B
This is simple submarine. She is small, maneuverable with great concealment and forward facing torpedoes.
She can't be underwater for long time, but she can replenish here air quickly(-> friendly towards beginners).   Type II   Tier V
Type U 66
Displacement: -surfaced: 791 t
                         -submerged: 933 t
Length: 69.50 m
Beam: 6.30 m
Draught: 3.79 m Speed: -surfaced: 16.8 knots
             -submerged: 10.3 knots Secondary armament: 1x8.8 cm SK L/30 naval gun
Torpedoes: -bow: 4x1 45 cm (17.7 in)
                    -stern: 1x1 45 cm (17.7 in) AA defence: Short range: none 
Quick history:
The Type U 66 was a class of five submarines or U-boats operated by the German Imperial Navy 
(German: Kaiserliche Marine) during World War I. The class is alternately referred to as the U-66-class or the Type UD.
The class was built by Germaniawerft of Kiel to their 506d design as the U-7-class for the Austro-Hungarian Navy. 
The five boats were sold to the Imperial Germany Navy at the beginning of World War I when it was thought impossible 
for the submarines to reach the Mediterranean for delivery to Austria-Hungary.
All five boats saw active service, and four sank 18 or more ships. Only U-68, sunk six days into her first war patrol 
in March 1916, had no successes. Two other boats, U-66 and U-69 disappeared in 1917. 
The remaining two U-boats, U-67 and U-70, were surrendered to the United Kingdom and were broken up by 1921.   Notes:
8.8 cm (3.5 in) SK L/30 deck gun, later replaced by 10.5 cm (4.1 in) SK L/45 deck gun   This is the only submarine from WWI in this tech tree (not counting premium). I wanted more WWI submarines, 
but I found it difficult to integrate these submarines. However, I think later, I could make alternative beggining of this branch,
where these submarines could be.
Why did I choose Austro-Hungarian submarine, that was in service of Germany? I wanted to prepare players for stern torpedoes.
Here is only 1, but later there are 2 for example (Type IX). If you don't want to use stern torpedoes, then you lose only 20% 
of your fire power (4 bow, 1 stern torpedo tubes).
Later, for example on Type I or Type IX, you would lose 33% of your fire power (4 bow, 2 stern torpedo tubes).
This ship should prepare you for stern torpedoes on higher tier.   In World of Warships:
In comparison to previous tier, Type U 66 has more torpedoes, secondary armament (still, you shouldn't rely on secondaries),
speed, hitpoints an can stay longer submerged. However, this comes at a cost. She has worse concealment, worse damege per
torpedo hit, turning radius and takes longer to replenish her air.   Type U 66
Tier VI
Type I
Displacement: -surfaced: 862 t
                         -submerged: 982 t
Length: 72.39 m
Beam: 6.21 m
Draught: 4.30 m Speed: -surfaced: 17.7–18.6 knots
             -submerged: 8.3 knots Secondary armament: 1x10.5 cm (4.1 in) SK C/32 naval gun
Torpedoes: -bow: 4x1 53.3 cm (21 in) torpedo tubes
                    -stern: 2x1 53.3 cm (21 in) torpedo tubes AA defence: Short range: 1x20mm C/30   Quick history:
The Type I U-boat was the first post–World War I attempt by Nazi Germany's Hocheseeflotte to produce an oceangoing submarine.
Only two Type IAs were built. Although the boats did not have any major design faults, they were known to be difficult to handle
due to their poor stability and slow dive rate. The type was based on the design of the Finnish Vetehinen class and 
the Spanish Type E-1. The design later served as a basis for the development of other types of boats, primarily the VII and IX classes.
Constructed by Deschimag in Bremen, the first Type IA was launched on 14 February 1936. In 1940, the boats were called 
into combat duty due to the shortage of available submarines.Both boats experienced short, but successful combat careers. 
U-25 participated in five war cruises, sinking eight enemy ships. On 3 August 1940, while on a mine laying mission near Norway, 
U-25 struck a mine and sank with all hands on board. U-26 carried out eight war cruises, sinking three merchant ships and damaging 
one British warship on its first mission laying mines. On its second war cruise it became the first U-boat during World War II to enter
the Mediterranean Sea. On its eighth war cruise the boat sunk three merchant ships and damaged another ship the next day. 
The attack on this ship led to severe depth-charging by two British warships, including HMS Gladiolus. Unable to dive, U-26 
was forced to surface where she was bombed by a Sunderland flying boat. The crew scuttled the submarine and were rescued 
by Allied warships.   Notes:
Beginning of WWII submarines (not counting tier IV)   In World of Warships:
In comparison to previous tier, Type I has more torpedoes with better damage, hit points and surface speed.
However, she has worse speed, while submerged, worse concealment and maneuverability.   Type I   Tier VII
Type VII A
Displacement: -surfaced: 626 t
                         -submerged: 745 t
Length: 64.51 m
Beam: 5.85 m
Draught: 4.37 m Speed: -surfaced: 17 knots
             -submerged: 8 knots Secondary armament: 1×1 8.8 cm (3.46 in) deck gun
Torpedoes: -bow: 4x1 53.3 cm (21 in) torpedo tubes 
                    -stern: 1x1 53.3 cm (21 in) torpedo tubes  AA defence: Short range: 1x20mm C/30   Quick history:
These boats, designed in 1933-1934, were the first of a new generation of German attack U-boats known, as Type VII, 
they were popular with their crews and very agile on the surface. They also had a much more powerful striking power than 
the smaller Type II's. They had 5 torpedo tubes (4 at the bow) and would carry 11 torpedoes onboard or 22 TMA 
(=33 TMB) mines. They also had the effective 88mm fast-firing deck gun with about 160 rounds of ammunition.   Notes:
Maybe she could have 2 hulls- Type VII A and Type VII B? For now, she has only one- Type VIIA.   In World of Warships:
Even though Type VII A has one torpedo tube less, she has better DMP, thanks to faster reload. 
She also has better concealment. Her speed is slightly lower, but she has much better maneuverability than Type I
and more air.   Type VIIA   Tier VIII
Type VII C
Displacement: -surfaced: 769 t (Type VIIC)
                                              999 t (Type VIIC/42)
                                              769 t (U-Flak)
                         -submerged: 871 t (Type VIIC)
                                                1099 t (Type VIIC/42)
                                                871 t (U-Flak)
Length: 67,2 m (Type VIIC)
              68,7 m (Type VIIC/42)
              67,2 m (U-Flak)
Beam: 6.20 m (Type VIIC)
            6,85 m (Type VIIC/42)
            6.20 m (U-Flak)
Draught: 4.74 m(Type VIIC)
                5 m (Type VIIC/42)
                4.74 m(U-Flak) Speed: -surfaced: 17.7 knots (Type VIIC)
                                18,6 knots (Type VIIC/42)
                                17.7 knots (U-Flak)
             -submerged: 7.6 knots (Type VIIC)
                                    7,6 knots (Type VIIC/42)
                                    7.2 knots (U-Flak) Secondary armament: 8.8 cm SK L/30 naval gun (Type VIIC)
                                         none (Type VIIC/42)
                                         8.8 cm SK L/30 naval gun (U-Flak)
Torpedoes: -bow: 4x1 45 cm (17.7 in) (all hulls)
                     -stern: 1x1 45 cm (17.7 in) (all hulls) AA defence: Short range: 1x1 20mm C/30 (Type VIIC)
                                            1x4, 2x2 20mm (Type VIIC/42)
                                            2x4 20mm Flakvierling 38 (U-Flak)
                      Medium range: 1x1 37mm canon Flak M42 (U-Flak)   Quick history:
The VIIC was the workhorse of the German U-boat force in World War Two from 1941 onwards and boats of this type 
were being built throughout the war. The first VIIC boat being commissioned was the U-69 in 1940. The VIIC was an effective 
fighting machine and was seen in almost all areas where the U-boat force operated although their range was not as great 
as the one of the larger IX types.   Notes:
The Type VIIC/42 was designed in 1942 and 1943 to replace the aging Type VIIC. It would have had a much stronger pressure hull,
with skin thickness up to 28 mm, and would have dived twice as deep as the previous VIICs. These boats would have been 
very similar in external appearance to the VIIC/41 but with two periscopes in the tower and would have carried two more torpedoes.
Contracts were signed for 164 boats and a few boats were laid down, but all were cancelled on 30 September 1943 in favor of the 
new Type XXI, and none was advanced enough in construction to be launched. U-Flak
Four VIIC boats were modified for use as surface escorts for U-boats departing and returning to French Atlantic bases. 
These "U-Flak" boats were U-441, U-256, U-621, and U-953. Conversion began on three others (U-211, U-263, and U-271) 
but none was completed and they were eventually returned to duty as standard VIIC attack boats.   In World of Warships:
There would be 3 hulls- Type VII C - stock hull
                                      - Type VIIC/42 -better surface speed, more hit points but no secondary gun (compare to VIIC)
                                      - "U-Flak"- more hit points (but slightly less than Type VII/42)
                                                      - better AA defence
                                                      - Defensive AA fire consumable-> more survivable against CVs
                                                      - slightly worse speed, while underwater
All 3 hulls would have faster reload, slightly worse concealment and more air in comparison to Type VIIA.
I like, when players can choose their style of play.   Type VIIC   Tier IX
Type IX
Displacement: -surfaced: 1,032 t (Type IXA)
                                           1,120 t (Type IXC)
                                           1,610 t (Type IXD2)
                         -submerged: 1,153 t (Type IXA)
                                                1,232 t (Type IXC)
                                                1,799 t (Type IXD2)
Length: 76.50 m (Type IXA)
              76.50 m (Type IXC)
              87.58 m (Type IXD2)
Beam: 6.51 m (Type IXA)
            6.76 m (Type IXC)
            7.50 m (Type IXD2)
Draught: 4.70 m (Type IXA)
               4.70 m (Type IXC)
               5.35 m (Type IXD2) Speed: -surfaced:  18.2 knots (Type IXA)
                                18.2 knots (Type IXC)
                                20.8 knots (Type IXD2)
             -submerged: 7.3 knots (Type IXA)
                                    7.3 knots (Type IXC)
                                    6.9 knots (Type IXD2) Secondary armament: 1 × 10.5 cm (4.1 in) SK C/32 deck gun (all hulls)
Torpedoes: -bow: 4x1 53.3 cm (21 in)   (all hulls)
                    -stern: 2x1 53.3 cm (21 in)    (all hulls) AA defence: Short range: 1x2 20mm FlaK 30 AA guns (Type IXA)
                                            1x2 20mm FlaK 30 AA guns (Type IXC)
                                            1x1 20mm FlaK 30 AA gun (Type IXD2)
                      Medium range: 1×1 37mm (1.5 in) SK C/30 AA gun  (all hulls)
Quick history:
The Type IX U-boat was designed by Nazi Germany's Kriegsmarine in 1935 and 1936 as a large ocean-going
submarine for sustained operations far from the home support facilities. Type IX boats were briefly used for patrols
off the eastern United States in an attempt to disrupt the stream of troops and supplies bound for Europe. 
It was derived from the Type IA, and appeared in various sub-types.   Notes:
Type IXD was significantly longer and heavier than the IXC/40. It was faster than the IXC but at the cost of slightly 
reduced range. There were three variants: the IXD1, IXD2 and IXD/42.
Also- Tier IX is Type IX :)   In World of Warships:
In comparison to previous tier, Type IX has more torpedoes, better AA (but worse than U-Flak hull), more hit points, air,
better secondary armament, worse concealment, worse maneuverability.
There are 3 hulls: Type IXA- stock hull
                                Type IXC- more hit points, faster reload for torpedoes, slightly more air
                                Type IXD2-more hit points
                                                -slightly faster reload (but little bit worse than TypeIXC)
                                                -worse maneuverability and concealment (compare to both hulls)
                                                -faster on surface, slower while submerged   Type IX   Tier X
Type XXI
Displacement: -surfaced: 1,621 t
                         -submerged: 1,819 t
Length: 76.70 m
Beam: 8 m
Draught: 6.32 m Speed: -surfaced: 15.6 knots
             -submerged: 17.2 knots Secondary armament: none
Torpedoes: -bow: 6×1 53.3 cm (21 in) torpedo tubes   AA defence: Short range: 2x2 20 mm C/30 anti-aircraft guns   Quick history:
They were the first submarines designed to operate primarily submerged, rather than spending most of their time 
as surface ships that could submerge for brief periods as a means to escape detection. They incorporated a large number of 
batteries to increase the time they could spend under water, to as much as several days, and they only needed to surface to 
periscope depth for recharging via a snorkel. The design included many general improvements as well: much greater 
underwater speed by an improved hull design, greatly improved diving times, power-assisted torpedo reloading and greatly 
improved crew accommodations.   Notes:
The pinnacle of German engineering.   In World of Warships:
In comparison to previous tier, Type XXI has massive forward fire power (but no secondary armament), 
better concealment than Type IXD2, little bit more hit points (in comparison to Type IXD2), more hit points than Type IXA 
and Type IXC. She also has better maneuverability and more air (slightly), but most importantly - she has much better speed, 
while submerged.   Type XXI   Alternative branch
If you want more agressive style gameplay.
Characteristics of this alternative branch:
       -less hit points
       -less fire power and AA
       -much better concealment
       -less air, but with faster replenishment
       -fast torpedo reload
       -fast speed, while submerged   Tier IX
Displacement: -surfaced: 234 t
                         -submerged: 258 t 
Length: 34.68 m
Beam: 3.02 m 
Draught: 3.66 m  Speed: -surfaced: 9.7 knots
             -submerged: 12.5 knots Secondary armament: none
Torpedoes: -bow: 2×1 53.3 cm (21 in) torpedo tubes   AA defence: Short range: none    Quick history:
When development began on the Type XXI U-boat in late 1942, it was proposed to simultaneously develop
a smaller version incorporating the same advanced technology to replace the Type II coastal submarine.
The Type XXIII had an all-welded single hull, the first submarine to use such a design.
As with the Type XXI, the Type XXIII was intended to be constructed in sections, various modules being produced
by different subcontractors. Of the 280 submarines ordered, only 61 entered service, and only 6 ever carried out a war patrol.   Notes:
In game, speed on surface would be higher.
Maybe she could have freezing torpedoes (if you don't know, what it is, look at the Halloween event in 2018)?   In World of Warships:
In comparison to tier IX counterpart- Type IX:
Type XXIII has worse speed on surface and better speed when submerged and much better maneuverability.
Type XXIII has no AA or secondary armament. Type IX has more air, that replenises more slowly.
Type XXIII has better concealment.
Type IX has much more torpedoes, but they reload slower.   Type XXIII   Tier X
Displacement: -surfaced: 312 t
                         -submerged: 337 t
Length: 41.45 m
Beam: 4.50 m
Draught: 4.30 m Speed: -surfaced: 8.8 knots
             -submerged: 5 knots (electric drive)
                                    25 knots (HTP drive) Secondary armament: none
Torpedoes: -bow: 2x1 53.3 cm (21 in) torpedo tubes   AA defence: Short range: none    Quick history:
The Type XVII U-boats were small coastal submarines that used a high-test peroxide propulsion system, 
which offered a combination of air-independent propulsion and high submerged speeds.
The Type XVIIA submarines were found to be very hard to handle at high speed, and were plagued by 
numerous mechanical problems, low efficiency, and the fact that a significant amount of power was lost due to 
increased back pressure on the exhaust at depth. Also, the length to beam ratio was too low, resulting in 
an unnecessarily high drag. All three completed Type XVIIB boats were scuttled by their crews at the end of World War II.   Notes:
Type XVII B shouldn't have permanent speed of 25 knots, while under water. It would be hard to kill her.   In World of Warships:
Same armament as Type XIII, but with slightly faster reload and slightly more air. Big difference is speed.
She can have speed up to 25 knots (HTP drive), while submerged. This is little bit too much, so I think I have a solution.
This speed could be achived only, if "HTP drive" consumable would be active.
This consumable has infinite charges, but has cooldown of 60 seconds (+-, I can't say if it is too long or short...)
and it would be active for 30 seconds (again, don't know if it is too much or too short...).   Type XVII   Premium:
Tier V
Type U 151
Displacement: -surfaced: 1,512 tones
                         -submerged: 1,875 tones
Length: 65.00 m
Beam: 8.90 m
Draught: 5.30 m Speed: -surfaced: 12.4 knots
             -submerged: 5.2 knots Secondary armament: 2x1 150 mm (5.9 in) SK L/45 deck guns
Torpedoes: -bow: 2x1 50 cm (20 in) bow torpedo tubes   AA defence: Short range: none    Quick history:
Type U 151 U-boats were a class of large, long-range submarines initially constructed during World War I 
to be merchant submarines and later used by the Kaiserliche Marine (Imperial German Navy).
They had a cruising range of around 25,000 nautical miles (46,000 km; 29,000 mi).   Notes:
This wouldn't be the only premium submarine. Germany has many special submarines.   In World of Warships:
This submarine rely more on her secondary armament. Every other submarine has secondary armamenr more
as last solution, rather then a weapon.
She has more hit points, worse concealment, worse maneuverability than her tier V counterpart.   Type U 151   Summary:
This tech tree has can be divided into:
-starting submarines for begginers
-proper (and bigger) ocean submarines- Type VII
-high tier submarines- big ocean submarines and agressive submarines   General characteristics of this tech tree:
-good mix of maneuverability, speed, hit points (exept fo alternative branch) and torpedo armament
-submarines would have less hit points that destroyers-> the least hit points from game (exept for Type U 5151).
  However, thanks to small size and good concealment and mainly to ability to be submerged, they aren't that easy
  to kill.   Usually, I want to compare my fan-made tech tree to other branches, but here it is impossible.
If submarines would be implemented in WoWs, there would be a lot of changes:
         -captain skill
         -new anti-submarine warfare
         -new styles of gameplay
         -rework of maps
One thing is certain, if we will see submarines in WoWs or not, that will reveil only the time. If I could choose only 1 submarine, that I want to play, than it would be Type VIIC
    - classic German submarine, robust, efficient, time-tested...   German Tech tree- Submarines  
I will be glad if you leave your comment below. I hope you enjoyed this article and have a nice day.
I apologize for any grammar mistakes, english is not my native language.                  
Sources of information:
Encyklopedie válečných lodí- Naše vojsko
Německé válečné ponorky 1939-1945
https://en.wikipedia.org/wiki/Type_Type_U 66_submarine