This Machine Eats Fish.
On the surface, it's relatively straight forward: charge it up, let it spin, watch things explode. Under the hood, however it's... actually still pretty straight forward. But. It's a slow moving, slow charging weapon, and I think that tends to trip people up.
| Portion of Charge | Damage Done |
|---|---|
| 1/4 of first circle | About 300 |
| 1/3rd of first circle | About 400 |
| 1/2 of one circle | About 500 |
| Two Full Circles | Damage per shot bumps to 60 |
Table's a little different for this one. Each shot does 35 until you hit two full circles, and that's not that interesting. What is is how quickly you can get to a point Something Big Dies.
My table should quickly show the most important thing you need to know about the Hydra: while charging to full takes a while, most of the time, you don't actually need that full charge! You only need a measly quarter to kill a steelhead. A third takes out a single cohock. A half will clear a scrapper, slammin' lid, or steel eel. Anything charged beyond that means additional targets and/or the room to miss (or have something else take) a few bullets. Even if you just stick to learning the timing for half circle charges, you're going to have buckets of more freedom with this puppy.
As a heavy weight backline weapon, your job is still to hold back, though. Like the E-Liter, you want to find a position near the basket with some height where you can rain down ink--you just don't discriminate as much as a charger would. Small fry to steelhead, everything is fair game; charge up and unload on all within your range. Focus on high threats and anything that would force you to move, and let things come to you as much as possible. Splatlings bring the pain, but they're not nearly as mobile as a charger due to the inability to shoot-and-swim (more on that later). As the heaviest and slowest splatling, you will feel like you're moving through molasses. You're right, so stop moving as much as possible! Use small charges to clear out anything near you, then use the space to charge back up while the bosses close in.
As you play, focus on finding good positions, and remember the ones you find work well for you. Look for places with good exit points that will keep you able to hit a variety of targets. Keep track of basic paths, too, so when you're in a goldie seeking round you can find the spot that lets you unload a full two circles on that shining salmon!\
In general, what kills a hydra is getting trapped in sludge. There's no real bullet proof way to avoid it outside of everyone proactively killing bosses and inking the floor (and some rng in your favor never hurts there!), so it's important to know your biggest escape trick: the splatling line. I think I picked this one up from my buddy who mains splatlings; it's not intuitive, I think, but once you've done it, it makes a lot of sense and you'll want to keep doing it. What you do is charge up a bit (it varies per splatling, but for hydra I'd go with a quarter circle bare minimum), point your reticle down 45 degrees or so, and then bring it up to just above level in a smooth sweep. You don't wanna sweep fast, but it's not a slow motion either. You're looking to make a solid lane in front of you for swimming. Figuring out the fastest speed and minimum charge you can get away with makes this most successful; your aim is to paint a line faster than your passive dripping could do.
The other thing that contributes to your survival is knowing how and when to cancel your shots, since once you let go of your trigger, you're mostly stuck firing. (Some splatlings let you add more charge mid firing, but for the most part You're Just Shooting (and a lot).) However: you can cancel your stream by diving into your ink; all it costs you is a delay before your ink can fill back up again. If you're suddenly realizing that, like mr. skeleton, you should just walk swim out, dive and retreat. It's also nice when you realize your current salvo isn't quite gonna last long enough to catch that steelhead prepping to sneeze, but you think you still have enough time to get in a quarter charge if you cancel!
The hydra is an absolute beast when it comes to shredding things. Learn to love partial charges, practice splatling lines, and focus on your position, and you'll be a credit to your team.
Oh, also? This thing demolishes Cohozuna. Forget bosses unless they're too threatening to ignore; just fill up to two circles for max damage and unload. If all goes well, you'll be seeing those sweet sweet 13 scale drops! (If you don't have the hydra, try to aggro cohozuna and make sure the hydra has the space to shoot)