I know this should be a Mojang issue  but maybe you guys will fix it ?

Sealanterns: the recipe calls for Prismarine Shards & Crystals

There is no way to do this in survival mode. Nothing drops the shards. Can you make Prismarine drop the shards like Sealantern drops the crystals or maybe smelting prismarine to get the shards.

 Just a thought.