Guide:Duke Fishron strategies

Duke Fishron is a flying fish/pigron boss with very high movement speed and high damage, making it the most difficult boss in the game so far. It is advised to use life-draining weapons on him and high movement speed.

Terrain preparation
Make a very long skybridge to fight Duke Fishron. Somewhere around 700-1000 should be enough. Asphalt blocks are highly recommended. The basic goal while fighting Duke Fishron is to run away quickly while attacking constantly. Alternatively, you can build a very long zigzag pattern of diagonal blocks.

Multiple layers may assist in avoiding his attacks, though it's not entirely necessary. For example, a second skybridge of asphalt can be made a ways above the first. You can then switch between sky bridges, going left on one, flying up to the next level (or dropping down) and running back the other way. This method means that if you've spaced one bridge far enough above the other, you will never have to worry about his sharknadoes, they'll be gone before you return to the spot he dropped them. Switching levels can be tricky to do without getting hit, setting up floating bricks of dirt to warn you when your roads are about to end, and when you get to them switching to the rod of discord in case he gets too close can be very helpful.

If one desires not to spend time making an arena, they can use a Water Walking Potion instead.

Armor

 * For magic it is advisable to equip the Spectre Armor with the Spectre Hood to drain health, or mask if one desires more damage.
 * For melee characters the Beetle Armor with Scale Mail are recommended as they give decent defense paired with attack buffs which stacks as the player damages the boss or the Sharknados. If the player desires high defense, Beetle Armor with Shell or Turtle Armor are recommended.
 * For ranged characters the Shroomite Armor is highly recommended.

Magic

 * Homing weapons like Bat Scepter or Spectre Staff will let you focus on dodging.
 * Rapid weapons like Razorpine or Leaf Blower, or Razorblade Typhoon if you have already defeated the Duke, will let you focus on dodging as well, if you have decent enough aim.
 * The Golden Shower spell is helpful as it reduces his defense.
 * The Bubble Gun does very well if you have beaten him.
 * Tempest Staff provides a source of constant damage.
 * If you have good aim the Inferno Fork does a lot of damage.
 * The Blizzard Staff is very good for attacking while he is stationary.
 * The Rod of Discord isn't a weapon, but helps with dodging.
 * Any Minions can only help.
 * Avoid using magic weapons like Magnet Sphere, Wasp Gun, Rainbow Gun and Staff of the Frost Hydra as Duke Fishron's extreme speed will render these attacks nearly useless.

Melee

 * Vampire Knives with Flask of Ichor are very useful for stealing life and give debbuff ichor combined with decent damage, however the life steal effect seems to work better on his second stage.
 * If you have beaten him before and acquired Flairon you can easily beat him by flying away and spamming it.
 * Flask of Ichor is useful to slightly lower Duke Fishron's defense.
 * The Terra Blade also performs well, though not usually as well as the vampire knives.
 * Constantly throwing the Paladin's Hammer while flying around can defeat him quickly.

Ranged

 * The Snowman Cannon is powerful against him, if you have defeated the frost moon.
 * The Chain Gun, if you have beat the frost moon, or Megashark, paired with Chlorophyte Bullet do very well; as these weapons have homing properties little aim will be required leaving the player to focus on dodging the boss.
 * The Piranha Gun attaches to Duke Fishron and deals continuous damage, so the player can focus on dodging Duke Fishron's attacks.
 * You must do this at the start of the fight, or else he will be too fast for the piranha to latch on.
 * Ichor Arrows or Ichor Bullets will reduce his defense.
 * If you have defeated Duke Fishron already, the Tsunami with Chlorophyte Arrows is useful.
 * The Stynger is very effective.

Accessories
A must is Hoverboard and Lightning Boots or better as primary choice. They are both fairly easy to get at this point. If you have defeated Duke Fishron, Fishron Wings will also help. Frog Leg can be used for more mobility. A shield will prevent knockback from Sharknadoes.

Equip accessories with damage, crit, or arcane if using magic, modifiers. Accessories such as the Celestial Stone, Fire Gauntlet, Sniper Scope, and emblems will also greatly improve damage output. Warding accessories can be used if the player desires extra defense.

Cross Necklace or Star Veil is recommended as the boss speed might cause several heavy hits on characters should the boss catch the player. The Sharknados may also flank the player hitting them consecutively especially on Duke Fishron's second phase.

Spectre Armor characters should consider using Magic Cuffs or Celestial Cuffs as the damage dealt by any of Duke Fishron's attacks will most of times completely restore their MP allowing to attack constantly while restoring HP; although care should be taken as the boss high attack may do a quick work of reckless players.

Magic users should also consider the Mana Flower.

If you have difficulty dodging his charges and/or bubbles, invest some time in getting a Tabi or Master Ninja Gear.

Charm of Myths will both allow for increased regen and reduced time for the Potion Sickness debuff.

Potions and Buffs
As with any other Hardmode boss, it would be useful to prepare the following potions:
 * Greater Healing Potions are highly recommended, though not entirely necessary with life-draining weapons.
 * Greater Mana Potions are recommended for magic users.
 * Regeneration Potion and Ironskin Potion to survive. Two of each will last enough.
 * Endurance and Lifeforce potions for even greater survivability.
 * Pumpkin Pies will likely last the entire fight, and it's easy to craft.
 * Swiftness Potion helps you a lot to evade the Fishron and its attacks.
 * Wrath and/or Rage potions for a boost in damage output.
 * Magic Power Potion and the Crystal Ball's Clairvoyance buff for magic users is recommended.
 * If a player has no arena, they can just use Water Walking Potions.
 * Gravitation Potions can free up an accessory slot, but it's recommended to use Featherfall Potions with them.
 * Melee characters that are good at dodging can use the Tipsy buff/debuff.

The Battle
Duke Fishron will attack in three different ways during his first stage. He will try to charge into the player five times before summonning one of two projectile attacks: Duke Fishron will blow about 20 bubbles that follow the player at a medium speed. They explode and dealing damage on contact. These bubbles can be destroyed via any attack or projectile, however they can be hard to hit. In his other projectile attack, he will summon some liquid blobs by waving his fins that fall through platforms until they travel 1.5x the vertical size of the screen or impact with blocks. Then they will create 'Sharknadoes'- giant water tornadoes that summon several Sharkrons. The Sharkrons have limited flight range, are destroyed on impact with blocks, and can be killed by the player. After a projectile attack, he will proceed to repeat the cycle.

Basically, just shoot him while running around, jumping, flying, and go back to avoid getting hit. Don't run too far or he may despawn. A good way to avoid Duke Fishron's attacks is to fly up when Duke Fishron starts dashing, and drop when he gets close to you, which is usually on the third dash. When it uses detonating bubbles is not much of a problem if you run and dodge its attacks. If using gravitation potions, constantly fly up and down to stay out of reach. Tornadoes may be painful obstacles, but you can recover your health quickly if given enough time, and Sharknados are not a problem as they are more likely to die very quickly. Focus on popping bubbles when they spawn. Remember, KEEP MOVING AND KEEP ATTACKING, otherwise you will die.

When Duke falls below 25,000 health, he will stay stationary for a second, then his eyes will glow as he enters his second stage. His damage, speed, and defense increase significantly. His lunges become faster, and are only performed three times instead of five before executing one of his projectile attacks, which are also upgraded. The detonating Bubbles are now fired while Duke Fishron flies in quick loops, which leave a trail of the bubbles behind. Instead of several blobs that create Sharknadoes, he will summon one blob that chases the player, creating a powerful 'Cthulunado' upon contact. It will summon twice as many Sharkrons as in the first stage.

In Duke's second form, you have to be more careful as detonating bubbles spray everywhere. Also, keep moving as he's extremely fast and follows you. But the most important thing is to avoid bigger tornadoes because they can do massive damage-up to 150 or more, even with better armor. On the other hand, you also have to fire more accurately because Duke Fishron moves and dodges faster than before, and sometimes it can evade homing projectiles. Like before, keep moving and keep attacking.

Care should be taken even after the boss has been defeated as he might summon a last set of Sharknadoes, which can kill an unsuspecting player. Additionally, the loot can fall inside the tornadoes that Duke Fishron may have created, forcing the player to wait if they don't want to take damage.