iRO wiki says you should walk around the OASIS, not the pool.??Basically walk around the??grassy areas and palm trees, and basically around all the little ruined columns, and structures. Basically wherever there's plants and not sand. (I made that mistake when I was doing this quest too)
Like this:
Significantly bigger circles.
Of course that's just a rough path,??it's not close to exact, but it should help. Actually, now that I think about it, it looks like the palm trees in the map picture make a ring around the place too.