You get a message from a lion guy - he says his star (i.e. Clank) is nowhere to be found, and offers Clank a daily oil massage. Ratchet does the "you're breaking up" bit and turns off the transmission. You land on Aquatos, which is a very pretty dark blue oceanic world, set underground.

New weapon - flux rifle 75,000 - sniper rifle

You see Captain Quark's ship parked here - hmmmmmmm. Go into the little bubble to ride on in. You see Skid there, apparently his code name is "shadow dude". He has a hacker and joins your team. Note he does not get hurt, so don't worry about protecting him. Go along the path behind him killing the amoeboids.

When you catch up with him, go through the door. Kill the flame guy, and he'll he hack by the door for you. It opens out the bridge. I admit I was pretty disappointed here, I loved the hacking puzzles from the previous game. I wanted to do the hacking myself!!

Health nanotech 25. Go through the pathways blasting away. Finally you get to the water area. Jump on in. Use SQUARE to dive down, X to rise up. So swim along, swimming by the boxes to blow them up. When you get 40 that's the Search for Sunken Treasure bonus. They're not all in one area - there are other swimming areas too.

When you get to the other end, climb out. You get warned about a huge biomass. Go to the ladder and up into the pipe. There are more ameboids in here. When you kill the large one, you get a sewer crystal. You'll meet someone later who trades these for cash.

Stand on the red button to open the door. Shadow Dude joins you and opens another bridge for you. Fight and get to another door, open it up. At this point, two tubes are curved magnetic paths - the third goes forward. Kill the enemies in there. Head back down into the water, swim along. To one side is a titanium bolt.

Swim through, then go out and up the ladder. Health nanotech 27. Go down the hall and meet up with another giant ameboid. Kill him for another sewer crystal. At the end room, step on the red spot to let in Shadow Dude. Move along to a bridge area, and shoot the guards. Again, Shadow extends it for you. Get to the elevator and ride on up the tube. At this point, Shadow runs off. You now run into Slim Cognito, your black market salesman.

miniturret glove - 25,000
lava gun - 40,000

I got both for FREE by loading up my Ratchet and Clank 2 game here! :) :)

Now you can take the sub to nefarious's base or fly back to the start on the green spot. If you go forward, you see the ventilation shaft and split up.

Ratchet and Clank 3 - Up Your Arsenal Walkthrough