Who am I? I am a gamer that only plays LOL if I have time, which is only on weekends. Other than that, I play Overwatch, Starcraft, and etc. Honestly, you shouldn't expect too much out of me for this guide.

Nautilus has many pros and cons:
PROS:

Super Tanky late game
Mostly CC
A under rated champ, so you will most likely get him in ranked
Good engage,
Can excel in jungle, top, support, and even mid.
His Q can help you escape bad situations
Focuses the carry in late game with ult
Synergizes well with a lot of champs

CONS:

Easy to learn, hard to apply
Has no life steal whatsoever
The champions that do counter him counter him hard
His Q can't go through walls and sometimes doesn't pull you forward when hit terrain
You get harassed in lane a lot
Farm isn't great
Isn't tanky for the first 20 min of game (unless you're fed)
There are better champs with the same CC and more damage (Malphite, Maokai, Camille, etc.)
Isn't loved by Rito

When you are going for ranked, Nautilus is one of the best champs to use because he isn't picked to be banned or picked to be chosen. In fact, if you become OP with Nautilus, you basically can win all of your ranked games with the right team.

This guide was made under a limited time, so if you need any clarification on any of Nautilus' skillset, email me at set4352@gmail.com. If you notice any errors or if you want to and anything. Comment below.