Most anglers aren't really into sharkbites, but that's another story if you fish for achievements in Final Fantasy XIV.
Sea fishing gives you the chance to earn the title of shark hunter if your group of fishermen can cast 200 of these big fish. You will earn the Certifiable Shark Hunter Bonus and get the achievement worth 10 points: What Did Sharks Do To You?
It seems like the most difficult of sea fishing successes, simply because of the number of fish you will need to catch, but knowing when and where to fish will help you catch sharks by the handle.
Before fishing
Make sure you've unlocked Ocean Fishing, of course. You'll want to be level 80 and well equipped before you jump into this achievement. Having 800 GP plus a dozen Hi-Cordials means you can throw identical throw and double hook sharks to maximize your transport. Consider getting food that gives you even more GP for a short time, like HQ Peppery Popotoes. You will need a good supply of meaty worms to catch your share of sharks; The optimal route to earn this achievement has two stops where you'll still need to cast, so don't skimp on the bait.
You will also need a group of 7 other fishermen who are working for the same purpose. There are several FFXIV and Linkshells Cross-world Fishing Discords that can help you find other people to fill your party. Shouting chat in Limsa during fishing hours is the best way to get an invite to these.
Fishing routes
Talk to Dryskthota at the sea fishing docks in Limsa Lominsa to see the sea sailing schedule. The best route for shark success ends in the Rhotano Sea during the day, as this path is good for sharks catching at two stops along the route under normal and spectral conditions.
How to catch sharks
Your party will need Spectral Currents to appear at both stops in order to have the best chance of success. You can cast a Spectral Fish while looking for the sharks you need, so don't ignore the heavy tugs (!!!).
When you're in Galadion Bay before the spectral weather, use plump worms as bait. Tarnished sharks have a heavy tug (denoted by three exclamation marks) and appear approximately 24 seconds after launching. Use the identical cast to throw a second Tarnished Shark, but save the rest of your GP and don't use the double crochet. When spectral weather appears, keep using plump worms as bait. You can use Double Hook on heavy tugs (!!!) to catch 4 funnel sharks at a time, then use Identical Cast and Double Hook again. If you started with 800+ GP, you should be able to double them and get 4 more.
Quicksilver Blades count towards your total, but they're not worth the double hook because you can only catch two at a time. If you catch a ghost shark, use the same cast, then double hook the second hook to cast 4 more.
In Rhotano Bay during normal weather, continue to use plump worms. Here you will try for Chrome Hammerheads. These have a heavy tug (!!!) and can take 15-26 seconds or more to appear after your casting. Catch the first one normally, then use identical Cast and double hook the second.
In spectral weather, double hook all heavy tugs (!!!) to catch 4 executioners, then identical distribution and double hook again. Sweepers have an average tug (!!) and count towards success. They only double for a catch of 2 sharks, so save your GP for the executioners instead.
If you still have time after a spectral window, double-hook all the powerful tugs (!!!) you get; they are guaranteed either tarnished sharks or chrome hammerhead sharks. An identical cast and another double crochet here could put your group just over 200 sharks in a pocket if you just come up short, so don't give up!
Special thanks to S'yahn Tia de Cactuar for creating a Sea Fishing Tracker.