You have to use the car to collect the orb, the dark ring is a force field, to keep you from climbing the mountain without the car and the orb powerup. :V
Driving a car into the water is pretty unintuitive, in most games you lose the car or get a game over. Plus, if the car drops into the water at any angle less than a gentle slope, the car bobs around like crazy and it's almost impossible to regain control.
Also, I went up to the top of the mountain, got knocked off cuz I didn't know what to do, and now the car is trapped at the bottom of the ocean. Please just add a 'respawn' command to put you back at the start location or something, at least until the controls and the physics are more manageable.