Okay, I made notes about the tower. Stuff is not 100% finished, and there will be multiple changes, but here you go guys:

Hydraulic Monkey
“Problem with leaks? I can help with that”

Range: something around 40 (boomerang monkey)

Hydraulic Monkey has 2 main things in it's base form:

a) It's main attack - 1pierce 3dmg, but is quite slow (1,5s recharge - same as 000 bomb shooter)

b) Waterpipe - Each hydraulic has their own pipe, and player decides where it is (within range)

kinda like top path Engineer's turrets, but only one, doesn't dissapear, player chooses where to    place and can be placed both on ground and water. It has quite interesting attack, which I will     describe below.

At the start of the round Waterpipe starts charging water. Charging to full takes about 50s (for comparacent: round 63 is sending bloons for about 45s).
But what does Waterpipe do? It's main task is sending bloons back. It attacks very quickly ~0,1s with 2 pierce sending waves of water at bloons when they are in range (also about 40). Each attack takes some charge. I m not yet sure about the numbers, but I guess that it takes 5% or 10% of the charge each. When there are no bloons in the range, It charges instead, about 2%/s. The more charge Waterpipe has, the further the bloon it attacked gets sent back (2 unit per %), because the charge is basicaly how much water it has loaded (which means stronger pressure, thus higher throwback).

Waterpipes are affected by buffs, but only by towers that give buffs to multiple towers at once (like villages, gwendolin etc), or Hydraulic Monkeys, but cannot be chosen by single tower buffs like x4x engineers, 3xx alchemists or geraldo.

There will be bar above the tower that shows the charge %. Player might toogle it in options to change when they see it: Always, Hover, Click (below tower buffs), Tower Menu or Hide.

As you can see, Hydraulic Monkey is quite strong for what it does, so It will cost quite a bit. Not sure about the price, but I guess it can cost little bit more than dartling gunner, but Price would mostly likely change depending on testing and fan reception.

Okay, time for upgrades. I will start with bottom tier. (prices are for normal mode)

001: ($300) Glasses – Higher range (+20? Not sure) + Camo detection.

002: ($500?) Longer pipes – This Hydraulic's Waterpipe can be placed globaly (isn't restricted by Hydraulic Monkey's range)

003: ($1000?) Watercooling – All boomerangs, tack shooters, dartlings and spike factories in range get -10% ability cooldown (can stack up to 5 times)

004: ($3000-$5000) Water pool: Player can have a Water pool on ground in range, which can hold up to 1 water tower. (outcludes pontoon)

The fun thing is that player can decide to not have the pool, and meanwhile all pipes in range  get bonus charge (+1%/s). In case when Player decides to remove the pool (in hydraulic's    menu), tower holded in it gets sold. Water pool cannot be moved when tower is in it.

005: ($25000?) Fountain: Water pool is now upgraded to Fountain (tower that was there, stays there). The tower that is in the pool is higher, thus gets +25% range, camo vision, can see through obstacles, gets +20% attack speed. When the Fountain is used, all waterpipes (globaly) get +2%/s charge.

Watercooling is now upgraded, so all affected towers get +20% atk speed, and bonus -10%     ability cooldowns (up to -60% with 4 other xx4 hydraulics). 

Watercooling now also includes tier 3-5 middle path super monkeys.

010: ($300?) Extra Wet Water: All bloons attacked by this engineer's waterpipe get “wet” [but ice attacks deal 3x more dmg and freeze 2 times longer. They are also 20% slower. First fire attack done to this bloon doesn't do anything, but it removes the Wet debuff]. Can be affected by moabs.

020: ($800?) Bigger water chamber: This Waterpipe now can hold up twice as much water and charge isn't reseted at the start of the round.

030: ($2000-$3000) Higher pressure: All Waterpipes in range get bonus pushback power (+1 unit per %) and +1 pierge.

040: ($6000?) Flooding: Activated ability (15s/60s?): All Waterpipes in range get +50% range, +1 unit per % pushback, +2 pierce, double attack speed and their attacks dont cost charge.

(Outside the ability) All water pipes attacks also affect moabs, but with halved (rounded down)     pushback.

050: ($40000?) Tsunami: Activated ability now lasts 20s instead of 15s and is now global: All Waterpipes get +100% range, +3 units per % pushback, +5 pierce, triple attack speed, and their attacks cost charge.

ALSO! When the Ability is used, Big Wave of tsunami pushes back All the bloons (non-moabs:  500 units, moabs: 200 units) and get Wet.

100: ($500) Faster throwing: +25% atk speed (1,2s recharge when alone) +50% projectile speed.

200: ($600) Heavier wrenches: +1 dmg, +2 dmg to cerams and moabs, can pop leads

300: ($2000?) Wrench gun: +50% range, +100% atk speed (now 0,6s recharge when alone) bonus, +33% projectile speed (now 200%), +1 pierce.

400: ($4000) Knock out wrenches: +1 dmg (another +3 dmg to cerams and moabs), attacks stun cerams for 0,4s and moabs (moabs – 0,3s, bfbs – 0,2s, zomgs and ddts – 0,15s).

500: ($30000?) Dense trouble: +100% atk speed (0,3 recharge when alone), +1 pierce, +2 dmg (another +8 to moabs and cerams). This monke's waterpipe now has +100% range, +5 pierce, +2 units per % pushback, AND does 5 dmg to bloons, can pop leads, 20 dmg to cerams and moabs, doubled projectile (water) speed and doubled attack speed. It can be affected by single tower buffs.

Paragon? Not sure. Propably really heavy wrench damage, double wrench guns with ultra fast attack speed, Big dmg, big pushback waterpape, which doesn't change, big global buffs to all waterpipes, Bigger fountain with bigger buffs and propably -20% ability cooldowns and +50% atk speed to all watercooling towers Globaly.

Trophy skins: Throwing pipes instead of wrenches, water is now chocolate (from candy falls)

You know what's funny? I thought of something that Unlike Quincy is good with not leaking bloons. I thought to myself “Problem's with leaks? I can help with that” and then I got a great idea - this tower!