1st screen:

Get here, and you'll see the place on screen 2.
2nd screen:

stand in one of the two areas (heard that you had problems getting up there from the first spot, so maybe the little filled red one is better
3rd screen:

Look at my minimap, and get there, now you'll see the waterfall, which you can jump in..
Congratulations... You're behind the waterfall.. Now begin waving at the people flying over you.
EDIT: Changed the pictures so that my name isn't shown anymore, and added a spot to stand in picture 2.






