Dire, Dire Docks - Koopa Surfin' Switch Star

This mission is unique to the Nintendo DS.
We should start the mission with Wario, to save time swimming through the tunnel and back. The Star Switch is under a black brick block on a sandbar in the first area. This is the main change from the N64 version. The middle block hides the Star Switch. The time limit is very short, so the only way to get the Star is by using the shell in the nearby item block. It took me two attempts to get it. The item block with the shell will respawn, so you don't have to exit the course.
Star Get #88, 7 Coins, 3 Lives
The next Star is the Red Coins in Goomboss Battle.

Dire, Dire Docks - Pole-Jumping for Red Coins

N64
It's time to finish the last two Stars in this course!
After beating Bowser in the Fire Sea, Bowser's submarine and the seal will be gone. The seal was concealing an exit to the moat outside the castle, and a current will draw you out if you're not careful. This mission took me four tries due to the current because I wanted to get the 100 Coin Star. To get the 100 Coins, I got the coins sloping down the rocks near the surface. The rocks are part of the wall that surrounds the first area. There are more coins underwater. By the time I exited the tunnel, I had 42 Coins. There are more coins underwater in the second area, including some near the exit where the seal was.
Now that the submarine is gone, poles are overhead. We use the same switch used to board the submarine to create two sets of stairs. We climb the taller set to reach the platform so we can reach the poles. We jump on to the poles and they will take us on set paths to the Red Coins, some of which are in midair. The Star will appear over the platform that is reached by three poles.
Star Get #73, 91 Coins, 13 Lives
One platform has a Blue Coin Switch, which brings our total to 100.
Star Get #74, 100 Coins, 13 Lives

Now that we've completed all the missions we can, it's time to access the top floors of the castle. We go up the stairs in the foyer up to the double doors and unlock them. There is another flight of stairs, with a Star Door at the top. We can open it at this point. Under these stairs is a Toad, who says "Thanks to the power of the Stars, life is returning to the castle. Please, Mario, you have to give Bowser the boot! Here, let me tell you a little something about the castle. In the room with the mirrors, look carefully for anything that's not reflected in the mirror. And when you go to the water town, you can flood it with a high jump into the painting. Oh, by the way, look what I found!" A Star appears.
Star Get #75, 0 Coins, 13 Lives

There is a Toad near a Bob-omb painting, who says "Thanks, Mario! The castle is recovering its energy as you retrieve Power Stars, and you've chased Bowser right out of here, on to some area ahead. Oh, by the by, are you collecting coins? Special Stars appear when you collect 100 coins in each of the 15 courses!" Thanks, but we already know that. On to the next course!

Nintendo DS
I also got the 100 Coins Star here. After ignoring the water striders, I got the coins in the first area, and made it into the tunnel after being drawn into the vortex twice. I had 43 coins when I entered the tunnel. I had 72 Coins after collecting all the Coins underwater. Using the Switch to activate the stairs, we reach the platform with the first Red Coin. They are in the same locations as the N64 version. I got some Blue Coins from the Blue Coin Switch and the Star appeared.
Star Get #79, 110 Coins, 2 Lives
The only major difference between the versions is that there is a platform in the DS version where you're supposed to jump to another pole while both are moving, which makes it easier. After I got all of the Red Coins, the Star appeared in the same place.
Star Get #80, 118 Coins 4 Lives
We get a message: "You've found 80 Power Stars! The mystery of the endless stairs is solved, thanks to you. Is Bowser ever upset! Now, onto the final showdown!"
Well, at least it's more accurate this time.
We unlock the door to the second floor. The Toads will give us similar messages to the N64 version, but they're customized for each character. I will cover them later.
The next mission is The Key to Wario.

Dire, Dire Docks - The Manta Ray's Reward

N64
In the first area, there is a manta ray swimming in a circle, leaving rings behind it. If we swim through 5 of those rings, a Star will appear over the whirlpool and the chime sounds. We do not have to be precise when swimming through the rings, but should be careful when trying to get the Star.
Star Get #71, 0 Coins, 4 Lives

Nintendo DS
In the same area, we have to swim through 5 of the rings that the manta ray leaves. The Star appears above the whirlpool. Not a lot of precision is needed for swimming through the rings, but we should be careful near the whirlpool.
Star Get #76, 0 Coins, 4 Lives
The next mission is Bowser in the Fire Sea.

Dire, Dire Docks - Through the Jet Stream

N64
This mission is similar to "Through the Jet Stream" in Jolly Roger Bay. We swim through the channel to the other area. Near the seal, underwater is a grate with rings and a jet stream coming from it. After floating (or standing) through 5 rings, each with its own number, we hear a chime and the Star appears over the grate. The rings will continue to appear. Because of the jet stream, we need the Metal Cap to reach it. Run quickly, as the power does not last very long.
Star Get #70, 4 Coins, 4 Lives
We get a message: "You've found 70 Power Stars! The mystery of the endless stairs is solved, thanks to you -- and is Bowser ever upset! Now, onto the final bout!"
Well, we can now tackle the final Bowser with 70 Stars, but we can't reach him until we beat him a second time. We haven't even discover these mysterious stairs, and we've already taken care of the problem! This is what happens when you try to be thorough.
Nintendo DS
We need Wario for this mission. Wario is a slow swimmer, so watch your health meter if you start the course with him. We go through the tunnel and get the Power Flower. With the Metal Cap, we fall to the grate and stand through five rings and jump up to get the Star when it appears.
Star Get #87, 6 Coins, 3 Lives
The next Star is Koopa Surfin' Switch Star.

Dire, Dire Docks - Inside the Cage

This is a renamed mission unique to the Nintendo DS. The N64 mission title is Collecting the Caps...
We need Luigi for this mission. With Luigi, we swim through the channel to the other area. The sub is still there because we haven't beaten him yet. The Power Flower is on the same wall with the switch, closer to the seal. We get the Power Flower to vanish and swim down to the cage to the left of the seal.
Star Get #75, 4 Coins, 4 Lives
We're halfway done! Only 75 more stars to go! (The DS version has 150 Stars, while the N64 version has 120.)
The next Star is the Manta Ray's Reward.

Dire, Dire Docks - Collecting the Caps...

This mission title is unique to the N64.
This is a simple mission. All we have to do is swim through the channel to the other area, get the Vanish Cap, which is next to the Metal Cap, and swim with it to the cage to the left of the Bowser seal. Because I went out of order, and have not yet defeated Bowser, his sub is still there.
Star Get #69, 39 Coins, 4 Lives

Dire, Dire Docks - Chests in the Current

N64
I'm going to finish Dire, Dire Docks before I deal with Bowser. We dive down into the water to find the chests. We must approach them in the right order to open them. If we do it in the right order, an air bubble will appear to replenish health and the Star will appear. If we do not open them in the right order, we will be shocked. The first chest is near a clam shell. The next two are in order if you swim in a counterclockwise circle from the first chest. The last one is near the vortex. I was shocked a couple of times. We carefully approached the chest near the vortex to avoid being dragged in. The Star appears near the wall near the hole to the other area.
Star Get #68, 4 Coins, 4 Lives

Nintendo DS
There are only three chests in this version. I took damage from swimming into the manta ray. The first chest is near the clam and the second one is to the left of it, while swimming in a counterclockwise circle. The third chest is by the vortex. The Star appears in the same place.
Star Get #74, 4 Coins, 4 Lives
The next Star is Inside the Cage.

Dire, Dire Docks - Board Bowser's Sub

Dire, Dire Docks is the 9th Course.
If we go into the basement, we find a new course to the left, behind a Star Door. There is a rippling blue wall, behind which is an inaccessible hole. We walk into the rippling blue wall.
We land in the water, where the music from Jolly Roger Bay plays. Other than a wall of rock, there is nothing above the water of interest, so we dive down. Under the water, we find a shark and a vortex. There is a tunnel in the rock, which we swim through to reach the other area. When we reach the other area, we find a Bowser logo on a metal sheet blocking something. Floating at the water's surface is a large submarine with another Bowser logo. Once we get out of the water, the tempo of the music increases. We walk along the dock and find a switch. A set of breakable block stairs to the sub appear. We climb aboard the sub and find the Star behind the sub's hatch/ fin. You can't go into the sub.
Star Get #67, 55 Coins, 4 Lives
After we get the Star, the rippling wall moves back, so we can access the hole.

Nintendo DS
Even though there are two more Stars in Shifting Sand Land, we can't get the Switch Star just yet, which also prevents us from getting the Star after it. So, we will start Dire, Dire Docks until we can access those Stars.
We open the Star Door to the left of the door to the basement. We get a message: "The Power Stars have broken the lock Bowser put on the Star Door. Now anyone can enter the door."
The room looks the same as in the N64: a rippling blue wall with a hole behind it. We walk into the rippling blue wall.
The first area looks like the N64 version, except for the sandbars on the edges of the rocks. There also are no gentle slopes to the bottom of the water. We find the tunnel and swim through it. In the other area, the Bowser logo has been updated. On the dock, we find the switch we need to board the sub. The sub seems lighter in color, but otherwise the same. The switch produces orange blocks, and we board the sub, taking a hit from a Bullet Bill in the process. The Star is behind the hatch/ fin.
Star Get #73, 5 Coins, 4 Lives
The rippling blue wall recedes, making the hole accessible. We won't be going there for a while.
The next Star is Chests in the Current.