Ocean Gateway
Ocean Gateway
Unstable gateway
An unstable gateway to the Ocean Monument. Stack villagers on it and right-click to send them through. Fades after 3 days.
How to Get It
Other Ways
Find an Ocean Monument out in the world. The gateway fades after 3 days.
Inside
Three waves and then the 
Elder Guardian. Win and you learn the Ocean Portal. The loot can include:
Prismarine Shard
Cod
Gold Ingot
Trident
Golden Apple