Prismarine

Prismarine is an upcoming stone-like material that only will appear underwater. This block will have several variants, with the rough, turquoise gravel-like form as seen in the infobox being one of two known variants. The other variant, seen in the preview image, has the same texture but is brown. The preview image of Prismarine also contains Sea Lanterns, so the two blocks may have something to do with each other

Properties (Upcoming)
Prismarine will have variants (sea lanterns will not be one of them). Two types have been confirmed so far, the infobox one and a more brown variant in the preview.

Trivia

 * The name "prismarine" was created by Reddit user AjaxGb during a naming contest, where Jeb was looking for a name for the block.