You are the tank so you should be ahead of your teammates and you should be the one to initiate a team fight.

Only initiate when all your team is here.

It's easy with Nautilus activate your Titan's Wrath then auto attack ,hit different minion each auto attack to activate your passive.

Passive: Staggering Blow great as tease and CC.

Q: Dredge Line For tease , escape , start a team fight and catch runners.(try to pull your enemy into the torrent)

W: Titan's Wrath For farming , survivability and damage if ignored in team fights.

P.S: If the shield is gone you will no longer deal damage over time.

E: Riptide damage and slow.

R: Depth Charge Better if you cast it on enemy in the back so you can damage and knock up as many enemy as possible.once you cast it ,your enemy won't be able to escape from it even if he flash away.(didn't try it yet on vlad and fizz so I don't know)

The combo:-

1- Q Dredge Line=>auto attack Staggering Blow (For simple tease in the lane)

2- Q Dredge Line=>W Titan's Wrath =>auto attack Staggering Blow=> E Riptide => R Depth Charge => Q Dredge Line