Bedrock Edition 1.4.0

1.4, known as Phase One of the Update Aquatic, is a major update to Bedrock Edition that was released on May 16, 2018. It added many new features focused primarily around ocean-related content, such as dolphins, shipwrecks, fish, tridents, buried treasure, drowned, and many other changes and fixes. Some features were also fully implemented that were added through experimental builds from the 1.2.x updates.

Initially set to be released as 1.3, that number was skipped due to issues with version tagging on various platforms. Also, because of the sheer amount of content to be added in Update Aquatic in Bedrock Edition, it was later decided to split the update into two major updates, with things like turtles, conduits and bubble columns being pushed back to Phase Two (1.5).

Blocks

 * Stripped Wood
 * Slabs and stairs
 * New slabs and stairs for all types of prismarine-related blocks
 * Coral Blocks
 * Trapdoors, buttons and pressure plates
 * New variants based on separate types of wood.
 * Kelp
 * Dried Kelp Block
 * Blue Ice
 * Coral Fans
 * Can be placed on top of other blocks.
 * Dead coral fans
 * Generate and function much like regular coral fans
 * Sea Pickles
 * Player does not collide with it

Items

 * Trident
 * Heart of the Sea
 * Currently does not have any use yet.
 * Will be used to craft a conduit in a future update
 * Experimental : Nautilus Shell
 * Fish Buckets
 * Are named "Bucket of [Fish Name]" instead of "[Fish Name] Bucket" (like in Java Edition)
 * Bucket of Pufferfish has an unique texture, showing a pufferfish with the old texture in a water bucket
 * An empty bucket can also be used to obtain a fish bucket
 * Enchanted books
 * New books for enchantments used on tridents
 * Dried Kelp
 * Spawn eggs
 * Experimental : Drowned
 * Dolphin
 * Fish mobs

Mobs

 * Experimental : Drowned
 * Drowned equipped with trident will use a melee attack if target is 3 block or less from them.
 * Fish
 * Will sometimes drop bones when killed.
 * Cod
 * Salmon
 * Pufferfish
 * Inflicts to the player if they get too close to it.
 * Tropical fish
 * Dolphin

World generation

 * Buried treasure
 * Shipwrecks
 * Stripped logs generate as part of them.
 * Underwater ruins
 * Icebergs
 * Coral reefs
 * Ocean ravines
 * Underwater caves

Gameplay

 * Achievements
 * More achievements, which include the following:
 * Atlantis? - Find an underwater ruin (20G)
 * Ahoy! - Find a shipwreck (20G)
 * Castaway - Eat nothing but dried kelp for three in-game days (20G)
 * Me Gold! - Dig up a buried treasure (30G)
 * Alternative Fuel - Power a furnace with a kelp block (20G)
 * Sail the 7 Seas - Visit all ocean biomes (40G)
 * Sleep with the Fishes - Stay underwater for one day without a potion (30G)
 * I'm a Marine Biologist - Collect a fish in a bucket (20G)
 * Enchantments
 * New enchantments to add to tridents
 * Channeling
 * Impaling
 * Loyalty
 * Riptide

General

 * Option to toggle certain Education Edition features into worlds
 * When used on an existing world, the world will be copied and marked with "[EDU]" to distinguish from the original world, similar to Experimental Gameplay.
 * Cannot be disabled once world is made.
 * Marketplace
 * Added an Inventory section to the Store to manage all your acquired content
 * Added sorting and filtering to the Store

Blocks

 * Rails
 * Can now be placed underwater
 * Water has been overhauled
 * Updated the texture
 * Has a new behavior mechanic
 * A water source block can be placed inside of most non-solid blocks
 * Flowing water will still not flow into non-solid blocks
 * Blocks can be placed underwater without creating pockets of air around them

Items

 * Book and Quill
 * Default author now reads "Author Unknown"
 * Leads
 * Can now be attached to boats
 * All items will now float in water
 * Updated textures for the following fish items:
 * Raw fish
 * Cooked fish
 * Raw salmon
 * Cooked salmon
 * Tropical fish
 * Pufferfish

Mobs

 * Baby zombies
 * Will now burn in the daylight

Non-mob entities

 * Items and block drops now float in water
 * The Player can now swim through 1x1 holes
 * Added a new swimming animation

World generation

 * Ravines and caves
 * Are now able to generate underwater

General

 * Most of the new features introduced in 1.2.13 are no longer under Experimental Gameplay

Fixes

 * - Water flows down beside glass
 * - Transparent blocks underwater, when viewed underwater, have flowing texture
 * - Placing snow against the edge of a block places it two blocks away
 * Fixed several of the top crashes that occurred during gameplay
 * Fixed a crash that occurred when playing Truffletop Town and dying while using Elytra and Fireworks
 * Pick Block will now work in Survival mode
 * Players can once again resurface after tapping "fly down" arrow while swimming with touch control
 * Firework Rockets now appear in the Recipe Book when being searched for in Survival
 * will now clear items properly
 * The first mouse click after re-mapping an action to a key is now recognized
 * Improved messaging when there are no Old Worlds to sync
 * Leads can no longer be attached to Horses being ridden by players
 * Enchantment names can now be seen on the Enchantment Table screen with Pocket UI when using keyboard and mouse
 * Fixed helmets being visible after being destroyed by taking damage from a mob
 * Resource and Behavior Packs are now properly enabled/disabled on Realms when restoring backups or replacing worlds
 * Changes made to the 'Trust Player Permissions' setting during world creation will now persist after loading into the world
 * Ladders no longer appear as invisible blocks with collision when placed using '/setblock'
 * The surface of water can now be seen when viewing from behind glass underwater
 * Sneaking and jumping into water no longer prevents jumping or swimming upwards
 * Double doors once again display correctly
 * Fixed the texture of Dark Prismarine Stairs
 * Banners are no longer consumed from the inventory when placed in Creative mode
 * Pick Block will now pick the proper variant of Buttons and Pressure Plates
 * Glass once again renders properly at further distances and certain angles
 * Zombie Villagers created during world generation are no longer super fast
 * It's once again possible to eat Raw Fish
 * It is no longer possible to refill breath by swimming against ice
 * Fixed a redundant gray line at the top of the Drowned's legs
 * The Trident will now be thrown the direction the cursor is pointing when playing in VR
 * Pressing the 'Default Settings' button will now only affect the control scheme that is selected
 * Personal Game Mode is now fully applied in Game Settings when switched from Survival to Creative
 * The Ender Dragon will no longer get stuck if the player moves too far away. Silly dragon!
 * Dropped items can once again pass under top slabs
 * Image thumbnails and game modes for worlds and world templates will now appear when searching on the Storage screen
 * The book on the Enchantment Table screen no longer overlaps the suggested enchantment's name
 * Tall birch trees will once again generate in Mutated Birch Forests
 * Mobs will no longer rotate their heads 360 degrees while in Boats
 * Fixed water not rendering when viewed at certain angles near the surface
 * A controller tooltip will now appear when it is possible to place blocks underwater
 * All overhangs and floating islands will once again generate with grass or snow under them
 * Bryce Mesa biomes will now generate correctly
 * Fixed entering a Minecart from another Minecart
 * Blocks can no longer be placed with no other block to support it when sprint-flying underwater in Creative mode

Video
Video made by slicedlime: