Hi guys! This is my first guide so hopefully it's pretty good! My username is AStorm02 and I am currently in bronze 2. I have played Nautilus since lvl 20 and I currently have mastery 7. I've mained Nautilus jungle since the beginning and it is my best position with my best champ.
I play Nautilus as a roaming support that gets your team super fed. At lvl 3 you have your hook with all of your other abilities and it almost guarantees a kill or a summoner spell. Early game I recommend that you try to farm a lot or you will eventually fall off.

Passive
Nautilus's passive is Staggering Blow. When Nautilus first AA's a target, the target is rooted for a short period of time. The ability has no cooldown, but it can only be used against the same target once. Then it goes on cooldown for that one specific champion, minion, or monster.

Q
Nautilus's Q is called Dredge Line. Nautilus throws out his anchor and if he hits a champion, monster or minion; he pulls himself and the thing he hit towards one another until the meet in the middle. If Nautilus hits a wall with his Q, it's cooldown is halved and Nautilus is pulled all the way towards the wall.

W
Nautilus's W is called Titan's Wrath. When activated, Titan's Wrath gives Nautilus a shield based on a percentage of his max health while also doing AOE damage to everything around him while it is active. In addition to doing AOE damage, his AA's do more damage. One extremely important thing about this ability is that it can be used as an AA reset. This means that if you use Titan's Wrath right after you AA then you will have another AA almost instantly after.

E
Nautilus's E is called Riptide. When Nautilus activates Riptide, three waves of water spread out around Nautilus. Each wave slows and damages what they hit. If anything is hit by more than one wave, each additional wave does less damage and has a shorter slow. This ability is extremely important when it comes to locking down your target, because if they try to run they will be slowed for even longer.

R
Nautilus's ult is called Depth Charge. It is a point and click ability where you taget one person on the enemy team and you launch pulses of water that chase your target. When it hits the target, they are knocked up and stunned for a brief period. Also, while on the way towards the desired target, the pulses of water knock up and stun (for a much briefer time) anyone who is in its path on the other team.

Pros:
-Super tanky late game
-Tons of CC
-Very good ganks

Cons:
-Super slow farm early
-Not much DPS
-If counterjungled, can get extremely behind

Most people say that Nautilus is super mana reliant early on. I disagree. Most people start W on Nautilus when jungling because it gives you a shield. I find that the shield doesn't help reduce much damage because you have less damage so it takes longer to kill the camp. Also, it has an extremely large mana cost at lvl 1. I take E and start red buff. You have your top or bot lane help you as much as possible and smite. Then I go wolves blue and skuttle, smiting when I can. After this you can either gank mid, top or bottom, depending on which side you started.

A lot of Nautilus guides say that you should go 12/0/18 in the mastery page but I go 0/12/18. One thing that I think this effects greatly is your jungle path. When you take 0/12/18, I usually take Meditation which helps me keep my mana up in early levels without having blue buff that Nautilus is supposedly so reliant on. Sometimes though it is good to mix up your masteries, because if you take expose weakness then your damage output by your team is greatly increased. This sometimes means that 6/6/18 is also viable. If you do go 12/0/18, then I recommend that you reverse the jungle camp order. You start blue, wolves, red, skuttle. This allows for the same lvl 3 ganks but helps out with your early mana problems.

Your job as the initiator tank is to start fights and lock down the enemy carry. Your job is to also tank the bulk of the damage for your team. Since you have so much cc, locking down the enemy carry is fairly simple. Hit your Q, AA, E, W. This combo pulls someone in, roots them, slows them, and then adds in some extra damage.

One thing about Nautilus that not many people know about is that his W is an AA reset. This is useful for farming since it gives you a shield in addition to reseting your AA so you can keep smashing away at whatever it is your AAing. Also, nautilus's E hits in 3 waves, so you want to try to get your target running when you E so that all 3 waves hit them giving them a larger slow and doing more damage.

All in all, Nautilus is a very strong champion but he's not too overpowered. This means that he won't get nerfed for a while and he might get buffed. He is also a very good counter pick since many champions can't escape him, and if someone doesn't know how to play against him they will be destroyed. Also, currently tanks are in the meta. Having multiple tanks on the team allows for the team to not die as much, which also stops the enemy team from getting fed. Tanks are also good when they are built with damage. If you build some AP items on Nautilus then you start to do a massive amount of damage while also not dying.