Hydrocore

Hydrocore is a rare crafting reagent necessary for many high end Battle for Azeroth profession recipes.

Source
This item can be created by any crafting profession. One Tidalcore and a specific reagent (based on profession) may be converted to a Hydrocore.

In Mythic+ season 1, Hydrocores were obtained as a drop from the last boss in Heroic (not a guaranteed drop) or Mythic dungeons. As of the start of season 2, Hydrocores have been replaced with Tidalcore and no longer drop in dungeons.

Alchemy

 * Sanguinated Alchemist Stone
 * Potion of Herb Tracking
 * Vial of Obfuscation
 * Mystical Cauldron

Blacksmithing

 * Stormsteel Girdle
 * Stormsteel Legguards
 * Magnetic Mining Pick
 * Platinum Whetstone
 * Storm Silver Spurs

Enchanting

 * Disenchanting Rod

Engineering

 * AZ3-R1-T3 Bionic Bifocals
 * AZ3-R1-T3 Gearspun Goggles
 * AZ3-R1-T3 Orthogonal Optics
 * AZ3-R1-T3 Synthetic Specs
 * Makeshift Azerite Detector
 * Monelite Fish Finder

Inscription

 * Crimson Ink Well

Jewelcrafting

 * Kaleidoscopic Lens

Leatherworking

 * Hardened Tempest Boots
 * Hardened Tempest Leggings
 * Mistscale Boots
 * Mistscale Leggings

Tailoring

 * Embroidered Deep Sea Breeches
 * Embroidered Deep Sea Gloves
 * Embroidered Deep Sea Bag
 * Tough-hooked Tidespray Linen