Java Edition 18w15a

18w15a is the thirty-first snapshot released for 1.13.

Blocks

 * Blue Ice
 * Generates in icebergs.
 * More slippery than ice or packed ice.
 * Crafted using 9 packed ice.
 * Conduit
 * Crafted using 1 Heart of the Sea and 8 Nautilus Shells.
 * Can be activated by placing prismarine, prismarine bricks and/or sea lanterns in 5x5 open squares around it.
 * When active, will affect nearby players in water with the Conduit Power status effect.
 * A complete structure will fully power the conduit.
 * Emits a strong glow, at light level 15.

Items

 * Heart of the Sea
 * Used to craft conduits.
 * Not available currently in survival.
 * Nautilus Shell
 * Used to craft conduits.
 * Can be obtained by fishing.
 * Drowned can spawn holding a nautilus shell.

Mobs

 * Dolphins
 * Spawn in any ocean that isn't frozen.
 * Neutral mobs. Like wolves and zombie pigmen, dolphins will attack in groups if one is angered.
 * Can be fed using raw cod, but they don't breed.
 * Drop cod on death.
 * Play with nearby items by picking them up and dropping them after a very short moment.
 * Occasionally jump out of water like real-life dolphins.
 * Can also jump between disconnected bodies of water.
 * Chase after boats and jump over water surfaces.
 * Suffocate after spending too much time on land.

World generation

 * Icebergs
 * Generate on frozen oceans.

Gameplay

 * Conduit Power
 * Given when a conduit is activated.
 * Stops the breath meter from running out, gives underwater night vision and increases mining speed.
 * When active at full power, the range will increase and hostile mobs within 8 blocks will take damage.

General

 * Added 'Biome Blend' distance video option.

Blocks

 * Ice
 * Mobs can now spawn on top of ice.
 * Water
 * Has a new texture.
 * Now only blocks 1 light per block, instead of 3.
 * This only affects newly placed water.
 * Underwater vision from previous snapshots is gone; water is darker at lower depths.
 * Ocean variants have their own water colors, and the swamp water color has been changed.
 * In newly generated chunks, it's less likely to find frozen oceans next to warm oceans, etc.

Gameplay

 * It is now possible to swim through one block holes again.
 * The transition between swimming and normal state is now smoother.
 * Sprinting at the surface of water no longer makes you swim, instead you stay at the same altitude constantly.

General

 * Optimized fog rendering.

Video
Video made by slicedlime: