World 3 is called Ocean Side. The levels you find here are primarily water themed, which makes the Frog Suit ideal for many (but not all) of the levels. This world is much longer than the previous ones were, with nine levels and two fortresses.
The map contains multiple pipes. They have been colored here, pipes with the same color connect together. Another feature of this map is the bridges - they go up and down when you beat a level, and you can only cross them when they're down.
There are two Hammer Bros. here. Note that if the Hammer Bro is standing on the water on the world map, there will be a bit of water in the fight, which is a problem if you're small Mario. One awards a starman, the other awards a Hammer. Using the hammer on the rock next to 3-5 allows access to the canoe. You can use the canoe to sail to two remote islands, they consist of some mushroom houses and spade panels.
The mushroom house at the top left has only a Frog Suit. The other ones still have the traditional three-way choice, but, except for the one on the top-right island, have foregone the Super Mushroom in favor of the Frog Suit.
3-1
If you got the Frog Suit from the secret mushroom house in World 2, this is the ideal level to use it in. If you didn't, drop down at the very beginning to find a block with a Fire Flower.
Many of the pipes here have water currents which push you away from the pipe (these are marked on the map). Unless you have the Frog Suit, you cannot swim against the current.
The first enemy you'll encounter here is a Blooper. It just swims around in an attempt to hit you. Unless you are Fire Mario, you cannot hurt it, so just avoid it.
If you're not Frog Mario, at the part where the path goes down, swim to the surface and jump out of the water. Run over the wooden structure to get to a small hole where you can find another Fire Flower.
If you chose to go down, you'll soon encounter a Lava Lotus. These spit out small fireballs that move slowly and hurt you. Quickly swim past to avoid them. Above the second Lava Lotus, the left block contains a Fire Flower.
After the gray structure, drop down to come into an area full of note blocks that push you around. At the end, you'll find a brick block with a 1-up mushroom inside. It will soon fall into the pit below though if you don't collect it fast enough.
The pipe at the top right takes you to the ending area which is empty apart from the goal card.
3-2
In this level you'll encounter donut blocks. These blocks fall down if you stand too long on them, so watch your step.
The first block contains a Fire Flower.
Jump onto the wooden platform, and as soon as you see the wooden blocks, bump into them from the side to reveal a starman, which helps a lot against the Cheep-Cheep jumping out of the water.
The blocks on the way contain continuous starmen. "Continuous" means that they'll only be starmen if you're still invincible by the time you bump into the block (otherwise, it will be just a single coin).
When you see brick blocks over your head, jump to the third one from the left to reveal a P-Switch. This turns the coins below into brick blocks, get to them then jump to the left of the coin overhead to reveal a hidden 1-up mushroom. You can then jump to the pipe when the Piranha Plant is inside.
Behind the pipe there's a block with a Fire Flower. You need to fall into the water to get it.
The pipe takes you to the ending area. If you're Raccoon Mario, fly straight up to find a wooden platform moving around in circles. Stand on the left tip and jump when it's at the very left to reveal another 1-up mushroom.
3-3
The terrain in this level moves up and down constantly. In the water, there's a Boss Bass, which will try to eat you if you're too close to the surface, which means instant death. While you can kill him, he will just regenerate, so it doesn't help a lot.
Jump onto the first note block to make a Fire Flower fall down. To get it, stomp on the Koopa Troopa and kick its shell against the brick blocks to the left. You can then reveal a P-Switch which will allow you to get the Fire Flower.
In this level, you'll see red lifts that spin around. Watch out to not fall into the water.
The brick block in the air contains another Fire Flower. Beside it there are ice blocks, which you can kick around like Koopa shells. Use it on the brick block at the ground to reveal a P-Switch, jump on it to make the coins ahead form a bridge to the pipe.
Way past the pipe, there's an isolated platform with a 1-up mushroom. You can either fly there as Raccoon Mario, or try to swim over there (extremely hard).
The pipe leads to the ending area, which is empty apart from the goal card.
Fortress 1
Part 1
First, pass the two Roto-Discs and the Dry Bones by jumping over them.
This place is a small maze. Most of the doors just take you to a moat filled with Cheep-Cheep. If you want to see the miniboss, run forward and take the sixth door. This leads to part 2.
Taking the fifth door also leads into the moat, but on a platform where you can grab a 1-up mushroom.
Go all the way to the back and enter the last door to get to a bonus area (see below).
Part 2
If you took any of the other doors, you'll fall into the moat. Take any of the pipes, they all lead back to the same pipe at the beginning. The blocks here contain raccoon leaves.
If you took door six, you'll land at the top left platform, at the bottom door. Jump up to the top door and enter it to get to part 3.
Part 3
Run forward to meet Boom-Boom. This time, he has a new trick up his sleeve: once you stomp him once, he starts getting airborne. You must then wait until he swoops down on you to stomp him. Of course, you could just as well enter as Fire Mario and feed him five fireballs to avoid this.
Bonus area
You'll see a bunch of coins, but the obvious way through the holes reveals hidden blocks which block you off. Jump from the door, though, to discover another hidden block which allows you to go up to the coins to collect them.
