Prismarine

Prismarine is an upcoming stone-like material that only will appear underwater. This block will have several variants, with the rough, gravel-like form as seen in the infobox being currently the only known variant. 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). No variant types have been confirmed so far.

Trivia

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