At the Krusty Krab, body slam the target. A tent will appear and you will have the jelly fishing gear costume.
Mermaid man costume
In downtown (construction site), deliver Krabby Patties to Patrick and he will give it to you.
Reep blower costume
In Jelly Fish Fields, win the 100 jelly fishing contest. Your prize will be the Reep Blower costume.
Downtown: Letter tile
In the Downtown section, there is a specific letter tile that must be obtained by "shooting the bolts to cross the chasm". To get this, go to the construction site and to the area past the drills to where the water and barrels are located. Make
sure you are in the Mermaid Man costume. The area is just after you get past the drills, not the location where you delivered the Krabby Patties to the foreman. Instead, run to the right where there is another man. Look to the left and you will see a glowing red object on the wall. Use your water balls to hit it. It will drop a platform. Jump to this and repeat until you get the tile.
Downtown: Helping Sandy clean up trash
To get this letter tile, you must wear your Reef Blower costume. Sandy then appears somewhere on Shell Street in the Business District. Then, simply blow the trash into the sewer holes.
Before you find the last tile in Downtown, you must complete Sandy's Treedome, Jellyfish fields, Goo Lagoon, and get all the other letter tiles in Downtown Bikini Bottom. Go to Downtown and do not go anywhere else. Keep looking for Sandy until you find her. After talking to her, big balls of trash will appear. Dump them in the sewers and claim your letter tile. To roll them in the sewers, you can also use you Reef Blower.
Goo Lagoon: Letter tile B
On the to do list in Goo Lagoon, on the job where it says "To the crows nest", it really means the top of the old, junky ship wreck where you have a karate match with Larry the Lobster. Go to the part of the ship that is moving. When the pole gets low, jump on it. It will go high again and you will get a letter tile.
Goo Lagoon: Letter tile P
Use the following tip in the Beach Area to get atop the juice cart to get the letter "P". When you first enter Goo Lagoon, you will notice the bus stop that takes you back to Bikini Bottom. A short distance from that is a lifeguard and a lifeguard
tower. This is not the lifeguard tower referred to in the following steps. Further down the beach, you will find another lifeguard and lifeguard tower. SpongeBob actually asks this particular lifeguard if he can sit up in his tower. The lifeguard's response is something to the effect that he may not sit in his tower, and tells SpongeBob to, "Beat it, runt." This lifeguard and his successors are the ones you will have to defeat. You can use any of SpongeBob's costumes while battling the lifeguards, although it is easier in the Mermaid Man outfit -- pelt them with waterballs, as opposed to trying to land a belly-flop or hit them with the fishing net. After defeating the first lifeguard, a new lifeguard appears in a new tower. There are about five lifeguards to defeat, each one bringing a new tower, which essentially builds a bridge over towards the juice cart. Near the first lifeguard tower and along the shoreline, you will find two rocks close together. High jump up onto the lower of the two, then jump and glide to the other rock. From the second rock, you will be able to get to the first lifeguard tower by performing a high-jump and glide. Keep repeating this maneuver until you have crossed all of the lifeguard towers and make it on top of the juice cart to collect the letter "P". Coincidentally, it is easier to jump from on top of the juice cart to the umbrella near the shoreline. Leave this umbrella stationary. Do not use your Reef Blower on the pinwheel to start the umbrella gyrating. If you do, you will have a hard time getting the Sand Dollar on top of it. For that matter, you may have a hard time landing on the umbrella at all since it turns so quickly. Other notes of interest: If you become frustrated while trying to achieve objectives, and leave the beach area for any other area within Goo Lagoon, any extra lifeguard towers you created will have disappeared when you return to the beach area, leaving you with the original lifeguard tower and you will have to start over in defeating the lifeguards to get the other towers back. The same is true if you used the Reef Blower on the umbrellas to start them turning/gyrating. When you return from a different area, they will all be stationary, and you will have to use the Reef Blower to start them turning again.
The Dutchman's Graveyard: Extra lives
When you are getting "booty", look around where you find the booty. Whenever there is booty, there are some lives.
Midway games: Finding Plankton
Before you can get Plankton, you have to complete the Bikini Bottom, Down Town, Tree Dome, Jelly Fish Fields, and Goo Lagoon levels; and have to get all the other letter tiles at Chum World. Go to the area where the back entrance of the "Big Top" is located. You will see a black speck holding up a letter tile. That little black speck is Plankton. You will have to chase him. The best strategy for this is rolling. When you are directly behind him, jump. If you get him, you will get the letter tile . If you lose, he will yell and jump into a vent . You will then have to go back to where you started and try again. Do not try sneaking up on him from behind -- it does not work. Then, you get to go treasure hunting.
Tree Dome: Running on the Hamster Wheel
Before you jump on the Hamster Wheel, change into your "Fishing Gear" costume. Then, jump on the wheel and keep jumping until the timer reaches zero.
Defeating The Flying Dutchman
Dodge his attacks until he throws a lot of bombs. Pick one up, dodge the flying ghost he summons (if it hits you, SpongeBob drops the bomb), and throw the bomb at The Dutchman. Dodge his portal, then he starts his attacks over again. Repeat the bomb technique.
When the Flying Dutchman becomes whole from his ghost phase, fire a bubble at him to stop him from blowing fire. When the barrels come down from the bubble hit, activate the karate chopping ability Sandy gave you. Karate chop one of them into the Flying Dutchman before they hit the floor. Note: Doing this requires precise timing and good aim.