Captain Toad is on the shore where some Piranha Creeper live. Walk up the capsized boat that serves as a ramp and drop down onto the Piranha Creeper on the sand. The hole nearby has the first gem. Get back up on the other side, where there's a Piranha Creeper and an enemy with a plant on its head that spits rocks. When it isn't spitting rocks, you can pick it up and throw it. Go through the hole in the rock to the back. Rotate the camera so you can see back there and time your drop to land on the Piranha Creeper in the water. The second gem is here. Walk to the left to get out of the water. Climb the ladder and cross the bridge. The bridge will partially drop, creating a ramp down to a plant with the third gem. Walk back up the ramp and either dodge or defeat the Piranha Creeper circling the Star.
Special Challenge: Collect 70 coins.