Ever since I saw Nautilus, I knew he was not only really cool, but I'd be good at him. I bet most of you felt like that. As soon as he came out, I bought him and destroyed the competition. Some said that Nautilus was OP, but after fighting against other Nautilus players, I confirmed that it takes skill to be a good Nautilus. I eventually decided to do my own build, since he was now one of my mains, and I use it all the time. Any other build I do doesn't work as good as this one. It's probably not the best, but it seems to synergize with me the best. Now, you'll notice that I don't talk like a pro, and that's because I'm not. But we all gotta give it a shot and get better before we can become pros, so this is where my builds start. Welcome to my first build on Mobafire!
Note: The build that I am suggesting is assuming the enemy team is a balanced team, such as 2 ad, 2 ap, and 1 tank. The 2nd build is for teams that have much more AP, and the 3rd one is for teams made up of AD mostly.

Pros
-Good jungle (jungle build won't be covered)
-Strong Tank
-Ult does more damage the more enemies run
-E does more damage the more enemies run
-More health=better W shield
-Epic
-Super cool giant with awesome powers
-Can swim in the air
-Best. Dance. Ever.

Cons
-Slowest character in the game
-Easy to kill when ganked
-Only need to hide behind minions to block Q

I think the masteries are understandable, so I skipped to Items.
Doran's Ring is a great starting item. Keep until you need to get your Guardian Angel or you need instant money, but try to keep it as long as you can.
Heart of Gold gives you health AND helps you buy everything else. Keep until you need to get your last item.
Mercury's Treads are magic resist, good for tanking. Also, Tenacity weakens CC on you, which is useful for tanking and/or running.
The Frozen Mallet offers a lot of hp, as well as extra crowd control. Constant whacks will easily get you an assist.
Warmog is continually growing health. Great for his W and surviving. Get another one for even MORE health.
Thornmail is excellent armor, and does decent damage against hard hitting ad carries. It is good for both an Anti-AD build AND the balanced build because a good balanced team will most likely have an AD carry. Only switch to anti-AP or AD if one of them outnumbers the other.
This increases health regen, as well as magic resist. a wonderful tank item.

Time to talk runes.

Greater Mark of ResilienceThis will help from th


Greater Seal of Vitality
Nautilus' W relies on health. Also, more health means more survivability.

2 Suggestions for Glyphs.
Greater Glyph of Shielding
Great for tanking mages. This is best for games with alot of enemy AP. I suggest this one.

Greater Glyph of Intellect
This is for games you really have trouble with getting out of mana.

2 Ideas for Quints.
Greater Quintessence of Vitality
More HP is good for him anytime. I suggest this one.

Greater Quintessence of Defense
Good for tanking AD enemies.

Guardian Angel supports survivability, but it is best for carries and/or people who would likely recover after resurrecting. It has good armor, but it is best for AD carries.
Banshee's Veil is good for teams with ridiculously powerful attacks or enemies who will use their ult immediately. Suggested for anti AP build.
Randuin's Omen can be built out of your Heart of Gold. It is a very useful teamfight power if you use it's active, too bad I'm never paying attention to that stuff.
Aegis of the Legion is a team buff power. Useful.
Quicksilver Sash ends all CC. MUCH more useful than Cleanse since it takes a spot in items instead and also comes with stat increase.
Locket of the Iron Solari gives a useful aura and active. Uses Heart of Gold.
Soul shroud gives extra health and an aura. Good Nautilus item.
Spirit Visage gives health and Magic Resist, as well as lowering cooldown and increasing regen.

Here I'm going to make up scenarios and give you a good item solution. The best items to replace in my build are the Frozen Mallet or Thornmail, so more than often those are replaced.

Scenario 1: The enemy is ALL AD. They barely have any CC, and just do a lot of AD damage. Magic Resist is mostly useless.
Solution: Follow the anti-AD build.

Scenario 2: The enemy is all AP. They have good CC, and just dominate with their magic damage.
Solution: Follow the anti-AP build.

Scenario 3: The enemy has CRAZY CC. They destroy everyone using all their stuns, slows, fears, etc.
Solution: Replace Frozen Mallet or 1 Warmog with Quicksilver Sash or Banshees Veil.

Scenario 4: The enemy is stacking Armor and MR.
Solution: 1, tell your team to buy more pen. 2, replace Frozen Mallet for Zeke's Herald (making them do more damage faster on enemies). To tell you the truth, if the enemy is stacking armor and MR, I would only do step 1, because faster damage isn't exactly going to fix everything.

Scenario 5: Your allies have mana problems in teamfights.
Solution: Replace Frozen Mallet with Soul Shroud.

Scenario 6: You got a legendary?
Solution: Perfect time to lose one of those Warmogs and get Leviathan instead. Still, you're a tank and shouldn't be getting much kills so... not a likely scenario.

Scenario 7: The enemy team can 1v1 any of your allies and beat them in seconds.
Solution: Replace Frozen Mallet with Locket of the Iron Solari, and replace any item with Aegis of the Legion.

Tell me any other Scenarios you can think of in the comments.

Not much to explain.
Q- You only need Q for its pull. The damage happens AFTER you pull them, when you get the chance to hit em' with everything you have.

W- Keeps you alive, longer and longer. Useful, and needs to level up with E. This power will keep you strong when tanking or dealing tons of damage.

E- Main damage source. Every tank needs damage, and this is your main source for farming as well.

R- You should always get your ult as soon as possible. This is useful for chasing, as well as damaging minions the person may pass along the way. Also, It is good for helping allies kill running enemies. Stun = good.

All good choices are in green, except my favorites in blue.
Flash- Good for chasing, running, etc. VERY useful.
Teleport- Very useful for getting around. Nautilus is the slowest character in the game.
Ghost- Faster. This is an excellent replacement for flash, but I prefer flash because it brings you to your target immediately AND can go over walls.
Exhaust- Slows enemies. Useful for chasing and running.
Smite- If you're jungling, it's a priority.
Ignite- Useful to finish enemies.
Heal- Luxury. I don't like this power. Heal should not be needed for a real skilled player, and it just trolls and annoys everyone.

Clarity- I wouldn't say it's a good choice, because most mana problems are only at the beginning.

Surge- Attack speed is useless to Nautilus.
Edit: Actually, If you are jungling, attack speed is quite useful. However, this is not a jungle build.

Revive- In my opinion, worst ability. It has an insane cooldown and barely does anything. The only time it's useful is very late game when one team is inevitably going to lose.

Cleanse- You shouldn't sacrifice a summoner spell for a CC clear.

Promote- I don't think it's that useful. All it does is make a single minion stronger, not so special.

Clairvoyance- Wards can replace.
Edit: Alright, it CAN be useful when things aren't warded. If you're the only support on your team, you might wanna take it. I usually don't unless I'm going full on support, which I never do as Nautilus.
And Garrison is Dominion. It's pretty useless, too.

1. Hook, Line, and RIPTIDE
Use your Q to pull an enemy in and use E immediately. Also, use W before hand to take less damage as well as do some extra when they arrive.
2. Water chases for you
If an enemy is at low health and starts to run, use R to finish them off. No chasing required, water chases for you!
3. RQWE
If an enemy refuses to get in range, use R to stun them, use Q, and unleash the darkest depths on them.
4. Wall Gank
When an enemy can easily be killed if you can just reach them, go behind a wall nearby and use Flash to unexpectedly gank them. As soon as you're on the other side, use Q and destroy them.
5. Pull Me Up!
If running, W, Q, and Flash are very useful. Use W to absorb damage, and throw your Q at terrain to go forward faster. Burn Flash if needed.

So, Nautilus is a tank, right? Then he has to be a team player. Here's some strategies you can do with your team:
1. Pull the enemy into your team. He won't be pulled in fully, but enough for everyone to use their spells. This is so simple, yet so effective. It should be obvious too. You also can do so to initiate fights.
2. Stun for allies. If an enemy is getting away and you know your ult can't kill them, do it anyway! Your allies, if nearby, will then have enough time to go in for the kill.
3. Slow them down with E. If you used trick 1. and the enemy somehow is surviving, then use E to do some damage and slow them down. Like trick 2. it will give allies more time to kill.
4. The most surprising... TANK! Pull them in, use W, and whack them once. They'll really wanna kill you then. Be a giant steel wall while your allies hit the enemy from behind you.
5. If your teammates can't kill the champion, don't just stand there. Use everything you got to kill them yourself!
6. Sacrifice. If your ally is low on health and you and that ally are being ganked, don't let your ally suffer. If necessary, go Leeroy Jenkins on them and die to save them. Trust me, if you run in on a silver platter, they will usually attack you instead of your running ally. They like the easier prey. It's better that the tank dies than anyone else. I have done this countless times and it has been worth it every single time - except when your teammate is dumb enough to just come back to save you, and I'll be honest... I've been that dumb teammate a few times.
7. You can achieve the same goal in 6. while still surviving. If enemy champions refuse to attack you and just chase your low-healthed ally, then use Q to pull them back and just annoy them until your ally is safe. Because they spent the whole time chasing, they (and you) are probably near a turret. Hit W and try to escape yourself!
8. Take the Skillshots. A good example is Ashe's ult. If Ashe uses her ult in attempt to kill a running, low-healthed ally, then don't hesitate. Hit W and get in the way to take the shot. Some other good examples would be such as Caitlyn's ult, Morgana's snare, and Ezreal's Q.

So, how's the best way to farm? it's easy. Just walk into a large group of minions, and press E. E does some great damage and is AoE, which is wonderful for farming. Simple as that. If enemies are farming there, then scare them by (almost) hitting them with Q or actually hitting them. If you keep throwing Q, they'll be scared and possibly back off a bit. However, don't use Q and hit them right away, they might be stronger than you. Don't forget to try and take blue to farm faster. Also, W makes your basic attacks AoE, so when you need gold or exp fast, or even need to push, use W to farm a lot.

Hey, kids! Remember to be a good tank! Keep increasing HP, armor, and magic resist!

As you see, I am no pro, but I wanna show you how I do well at tanking with Nautilus. He is of my 5 main champions (about tied with Xerath as my best) and I love playing him. This isn't an in-depth guide, but this is also my first Mobafire build, so do not treat it harshly. I have won many games with it, so I have faith in this build. Reply and tell me if you like it. Thanks for reading!