This level is only available when there’s a Purple Comet in orbit of Deep Dark Galaxy. This can only occur once you’ve completed the main story quest in the game.
Collect All Purple Coins
Before you head off towards the ship, you’ll want to collect the coins nearby the starting location. At the bottom of the water, you’ll find 10 in a circle on the ground. Then, you can find another 1 near the back wall and 2 underneath the starting platform. When you head back up onto the starting platform, you can get another 1 coin. To the right, you’ll find 2 extra coins to grab near the boxes. One is just on the edge of the water, and one high in the air that you’ll need to grab via a backflip.
Then, on a dock just to the left, you can find an extra 1 purple coin. Head over, past the Ghost Ship towards the left wall, where there are multiple ledges. On the ground level, you can find 2 Purple Coins, then you’ll need to jump up to the slightly higher ledge to grab another 2 coins. From there, backflip onto the ledge above, and walk along it to grab a further 3. On this level, you’ll be able to backflip onto two separate higher ledges. On the higher ledge to the left, you can grab 3 coins (including one you need to backflip for) and on the ledge to the right, you can grab another 4 (also including one that needs to be reached with a high jump). At this stage, before you head onto the Ghost Ship, you should have 31/100 Purple Coins.
On the wooden crate steps up to the ghost ship, you can collect another 3 coins. On the main deck area, you can pick up another 13 coins. When you head up to the right to the deck below the crow’s nest, you can pick up another 8 coins, bringing your total to 57/100. There are also 2 fairly hidden coins right beneath the floor of the crow’s nest. To grab them, backflip then wall jump against the wooden mast and then finally spin to get a little higher so you can grab the hidden Purple Coins.
When you climb up the pole up towards the crow’s nest, you’ll want to jump off at the top and fall into the 3 Purple Coins to the left. There are then 10 in a circle on the crow’s nest platform. And an extra 1 that you’ll need to backflip for in the centre of the nest. At this stage you should have 71/100 Purple Coins.
Before you head into the water to grab the final coins, you’ll need to long jump over to 1 Purple Coin just north of the crow’s nest. When you land in the water, you can find another 8 Purple Coins on the left side of the ship. At the back of the ship, beneath the crow’s nest, you’ll find another 3 coins just above the water.
From the bottom of the back of the boat, swim under the ship and grab another 9 coins, bringing your total to 92/100. There will be some on the ground and some near the bottom of the boat. Now, you’ll need to swim to an underwater platform near the short of the cave, where you can find another 3 coins. And finally, you can collect the last 5 on the surface of the water near the front of the Ghost Ship. When the Power Star spawns, you’ll need to hop back up onto the Ghost Ship’s main deck to finish the level.