I'm guessing your world was generated in an earlier version. Map generation changed significantly back around 1.7, and as a result biomes often got wonky when those worlds were brought into newer versions of the game (extreme hills labeled as deep ocean and other such nonsense). This can result in some crazy stuff like desert temples in rivers, ocean monuments in ravines, or even guardians spawning with no monument at all. One of the popular youtubers even found guardians on land in one of his old worlds (I think there was some water nearby).
You should build a small pool of water and see if guardians spawn. 3x3x2 should be enough. If it works, you could build a guardian farm in a ravine.
I use mods, but none of the mods I use would spawn this insane 'ocean' monument. Quite the discovery, I've never seen anything like this!
For anyone wondering, the texture pack I use is BDcraft 128x, and the shader pack I use is Sildur's Vibrant Shaders.
Sadly, there was no gold or anything, just the prismarine. Still very very cool!
I'm guessing your world was generated in an earlier version. Map generation changed significantly back around 1.7, and as a result biomes often got wonky when those worlds were brought into newer versions of the game (extreme hills labeled as deep ocean and other such nonsense). This can result in some crazy stuff like desert temples in rivers, ocean monuments in ravines, or even guardians spawning with no monument at all. One of the popular youtubers even found guardians on land in one of his old worlds (I think there was some water nearby).
You should build a small pool of water and see if guardians spawn. 3x3x2 should be enough. If it works, you could build a guardian farm in a ravine.
oh yeah, just a note, I use Biomes o Plenty so if anyone wants this seed you have to get that mod :/
strangely enough I generated this in 1.12, this is a very new map. I suppose this was just a very rare occurrence