This circle took me forever to find, the other comments said all this different stuff so i got confused, basically after reading them all a couple of times, one you walk through the cave to enter Lost Rigger Cove go along the coast line untill you get to the warf, swim around the 2 ships at the warf and walk past the ship thats being built, then u will get to a fence and a cannon, follow that fence untill it stops there should be palm trees around you, and if you keep walking straight ahead...a teensy bit to the left is the circle of rocks which looks more like a swirl when you get closer to it, summon the elemental, either kill him or run off and your done :)