This page offers a guide on grabbing the Shine Sprite in Episode 10 of Ricco Harbor. This area is accessed via the Rainbow M on the side of the Boathouse on the west side of Delfino Plaza once you’ve obtained at least 3 Shines and defeated the Polluted Piranha.
There’s another Shine to nab at the Surf Course under the tunnel at Ricco Harbor so in order to reach it, be sure to choose Episode 2 from the Episode selection menu and then head to the right to jump on a Blooper and make your way back to the tunnel outlined in the Blooper Surfing Safari episode page.
The course remains the same with there being one main change needed for the secret Shine Sprite, you’ll have to beat the course in under 40 seconds. As such, you’ll almost certainly want to take the Pink Blooper for it’s extra speed and you’ll need to focus on cutting corners where possible and leaping over the two final corners, provided you don’t hit the obstacles, this time should be easily achievable and award you another Shine.