Pools of Carnage  

The Tide Octopi spawn in abundance off the North Western Coast. Swim aways of the coast towards the mountains. They are on the seafloor. Just watch out for the maurading Windfeather ^^^ Epicx(2) who patrolls up and down the coast occasionally.

These can be found in the ocean near the Antonica gate in the Thundering Steppes. There are very few at a time, so you will need to patrol the area and pick them off as they respawn.

May also be found in the ocean in the south-west, where the Watcher of the Fields stands, though this has not been confirmed