Minecraft: Java Edition - 1.13 (Update Aquatic)

GENERAL

 * All undead mobs now sink
 * Changed underwater visibility
 * Your vision will gradually increase the longer you're underwater
 * Overhauled world generation
 * Overhauled command parser
 * Added new world type "Buffet"
 * Allows you to create worlds with a unique biome
 * More features will come to the Buffet world type in later updates
 * Added a bunch of new sounds
 * Added three new pieces of music
 * Added underwater ambience sounds
 * Added a swimming animation
 * Press your sprint key underwater to start swimming
 * Added data packs
 * Allows you to edit recipes, tags, loot tables, functions, and advancements
 * Added new advancements
 * Some blocks can now be waterlogged
 * Use a water bucket on a block to surround it with water
 * Added an "Optimize World" button (singleplayer -> edit world -> optimize world), which upgrades an entire world from older version to the latest version in one go

BLOCKS

 * Added blue ice
 * Found in icebergs
 * Added coral blocks
 * Added coral fans
 * Added coral
 * Added conduit
 * Combine 1 heart of the sea together with 9 nautilus shells to create the conduit
 * Makes your life underwater a lot easier
 * Added dried kelp block
 * Combine 8 dried kelp to create a kelp block
 * Added kelp and seagrass
 * Normal pumpkins no longer have a face
 * Added carved pumpkin
 * Use a shear on a pumpkin to carve it
 * Added sea pickles
 * Added bubble columns
 * Use either magma blocks or soul sand to create a bubble column
 * Added wood block
 * Combine 4 logs of any type to create a wood block
 * Added stripped wood
 * Right click with an axe on either logs or wood to create stripped wood
 * Added prismarine stairs and slabs
 * Added variantes for all 6 types of woods for pressure plates, trapdoors and buttons
 * Added turtle eggs
 * Be sure to protect them from hostile mobs

MOBS

 * Added tropical fish
 * Added turtles
 * A friendly mob that lays eggs on beaches
 * Added dolphins
 * A neutral mob that will lead you to treasure if you feed it fish
 * Make sure to not hit them unless you want an entire pod after you
 * Added the Drowned
 * Hostile mob that can be found naturally in oceans and rivers
 * Can spawn with tridents
 * Zombies will convert into Drowned if they're underwater for too long
 * Added Phantoms
 * Get a good nights sleep if you don't want these coming swooping at you
 * Drops phantom membrane
 * Added cod, salmon, and pufferfish as mobs
 * Changed the horse model to be more consistent with other mobs
 * Removed Herobrine

ITEMS

 * Added tridents
 * The newest weapon in Minecraft
 * Drops from the Drowned
 * Works as both a melee and a ranged weapon
 * Added trident enchantments
 * Added the ability to catch fish with buckets
 * Added map markers
 * Hold a map in your hand and right click on a banner to create a marker
 * Added heart of the sea
 * Found in buried treasure
 * Added nautilus shells
 * Drops from Drowned and can be found from fishing
 * Added phantom membrane
 * Dropped by Phantoms and gives you the ability to repair elytra and used for Potion of Slow Falling
 * Added scutes
 * Dropped by baby turtles when they grow up
 * Added Potion of the Turtle Master
 * Gives you Slowness IV and Resistance III
 * Added Potion of Slow Falling
 * Added dried kelp
 * Added spawn eggs for all the new mobs

BIOMES

 * Added multiple ocean biomes
 * Added coral reefs
 * Added underwater caves
 * Added underwater ravines

STRUCTURES

 * Added shipwrecks
 * Added underwater ruins
 * Added icebergs