MASSIVE underwater base! I just took the "Minronn Milltary point Rindr" schematic and made it into an underwater base, made a few changes too. To add it to your world you will have to go find a spot in the ocean, then dig down to the very lowest layer of bedrock and paste it there. it clears out a large area around it so don't bother making a big hole for it. ENJOY!!
This is a 2x2 secret door, totally hidden on a wall !
You can change the stone with WorldEdit into another type of block, and change the lever by another open mecanism (for exemple button, light sensor, etc ...).