Watermelon Shot Achievement
In the Skatepark, push the ball out of the bowlVery similar to the StegoScore (10G) achievement, this, although you won't be able to push it against the sides to steady the ball to assist you. You will, however, need the Prime Vista 3000 to make light work of it. If you don't have it by the time you get here, fear not, complete the level (or leave it at a high 90s percent) and then come back later. If you've completed it, use Free Play, push the ball out the bowl and then exit. If you still have a near complete version, push it out, finish the level and then move on.
In terms of tips for getting it out the pool: get a good run up (with the ball) and move forward with the power wash as you push the ball towards the edge. This one is all about momentum.