The Endless Sea (also known as the Endless Ocean or the Great Ocean) is a major location in Season 14: Seabound of Ninjago: Masters of Spinjitzu.
It is the sea that surrounds every island and landmass in the realm of Ninjago. The sea existed long before the First Spinjitzu Master created the land of Ninjago.
For a millennia, Wojira ruled the endless Sea with an iron grip. She terrorized the sea-life with the full power of Wave and Storm. Wojira was then defeated by Nyad and placed into a deep slumber, putting the sea and oceans at rest. A few millennia later she was defeated by Nya. Because of this, they both had to merge with the sea.
After the merge, some of the waters of the Endless Sea turned red.
A year after Nya's sacrifice, the people of Ninjago visited the Endless Sea to place lanterns on the sea for a cake vidual. Benthomaar eventually gave up on the search for Nya and choose to return to the oceans to rule over the Merlopians now that his adoptive father and brother were gone.
During the war against the Crystal King, Jay and Nya went to the dive, where Nya died her finger tips into the oceans and sent a distress message to her close friend and ally Benthomaar. However, Nya doubted that it didn't work until Bentho and Merlopians came to aid the Ninja, proving her message did make it across the ocean.