This page offers a guide on the hidden episode, Red Coins in the Sand Castle in Gelato Beach. This episode is accessible once you’ve completed Dune Bud Sand Castle Secret. You can access this episode by going into Episode 1 again.
Spray the Dune Bud
First off, you’ll need to spawn in the Sand Castle again. There are a fair few Dune Buds on the beach but you’ll need to spray the one circled below to trigger the spawning of the Sand Castle. The Dune Bud you need is in line with the beached boat, so you’ll come across it fairly easily if you just head down the beach towards the boat. It is also adjacent to a piece of land that juts out into the water (this is where the Sand Castle will also spawn).
Once you’ve spawned the Sand Castle, head through its arch to begin the second half of this episode.
Collect all 8 Red Coins
To make the red coins appear, you’ll need to groundpound the big red button on the green platform just up head. The first 3/8 coins can be found along the falling sand path. The rest can then be found on the large structure at the end of the pathway. The sand platforms do eventually spawn back in, so you don’t need to worry about leaving yourself stranded if you step on too many bricks. The 4th coin is just up ahead under an arch. Then the 5th and 6th red coins are on the orange corner blocks to the left and right of the arch way.
Tip: The orange blocks won’t fall, so you can stay on them as long as you need!
And finally, for the 7th and 8th coins, you’ll need to climb up the sand steps to the left and right of the center of the structure to reach the coins that are floating above the orange blocks. Remember, you can wait on the orange blocks whilst the sand platforms spawn in again, so you can make your way from one end of the structure to the other. When you’ve collected all 8 red coins, the Shine will spawn on the green platform in front of the sand structure.