Build your own guardians!

-Killing an elder guardian should drop an aqua shard.

-Aqua shards can be used on sea lanterns to spawn a new mob: the marine. This mob has familiar spikes but cannot move. Putting a marine underwater slowly turns it into an elder guardian. This guardian is tame and never attacks you.

-Using an amethyst shard on an elder guardian causes it to drop an item, which could be:

40% prismarine bricks or variants

35% nautilus shell or glow lichen

20% prismarine crystal/ related items

5% aqua shard

This process is called re-configuration. I feel like it would make sense due to amethyst being calibration-related. The drop would count as waste material generated inside the guardian's reaction chamber. Re-configuration also heals guardians.

-Normal guardians have a small chance of spawning around an elder guardian if it is near prismarine-related blocks.

-Aqua shards can be crafted into heart of the sea.