I was in the 1.8 snapshot yesterday and i was looking for an 'Underwater Monuement'. I found one and explored it. It didnt seem to have much purpose. I looked around and the few interesting things in it i found were this:

1: Guardians only spawn here
2: Along with the 3 Elder Guardians, Guardians drop 'Prismarine' Which appears to have no function.
3: The only things that are valuable are the Wet sponges and The Gold 'Treasure' chamber.
4: ITs very hard to find the place, along with actually infiltrating, which requires many potions and getting past all the guardians.
5: What does this benefit? Only sponge and Gold. Thats what i say.

Post your comments below to say your opinion on this.

Thanks and please sub!