Thanks for this great mod! :)

Is prismarine something that you would be open to adding to the mod, or was it left out by design? I am happy to submit a pull request for it, but I wanted to check and see if it's something that you're interested in before doing the work or stepping on toes.

Prismarine was left out because it wasn't part of the original mod, this was basically an almost direct port from 1.7, with some code cleanup and minor tweaks.

Its more of I don't have a texture for it, so it doesn't exist.
And believe me, I cannot make textures.