By the time you reach Chapter Three in Serial Cleaners, you'll have mastered every character's abilities. That's a good thing, because this is where the game starts throwing you some serious curveballs. Bob's flashback mission to the late eighties, which opens the chapter, sets the tone.
In this mission, Bob is coming off a serious bender. The cops and civilians he encounters are imaginary, but will still cause the mission to fail if they catch you. They can spawn and despawn as you move throughout the level, so always stay on your toes!
Middle Deck
Bob starts the mission on the aft deck of the ship. Climb down the ladder to your left and collect the evidence there; a cop will appear in the spot you just left. Keep an eye on their route, then climb back up and go to the right. You'll see another cop inside the aft cabin; clean up the blood on the deck before continuing.
When you reach the fore of the ship, a third cop will spawn near the body there. Wait for them to face away from you, then grab the body and bring it further aft. You can safely toss it overboard at the nearby drop point.
Return to the foredeck and clean up as much blood as you can without alerting the cop. You'll probably have to leave a few spots, but you can make up the difference later.
If you enter the cabin nearby, you'll find a large trophy that needs to be disposed of. As you approach it, a cop and a civilian will immediately spawn nearby. Move to the right, behind the civilian, and you should be able to slip out the door and toss the trophy overboard without being noticed.
Re-enter the cabin and make your way aft. The cop patrolling this area spends lots of time in the smaller rooms to your right, so you have plenty of time to remove the blood, wrap the body, and get it overboard. Use the double doors to the left if you need to make a quick getaway, but beware of the cop outside.
Upper Deck
You can go upstairs via the cabin or the spiral staircase on the aft deck; there are several bodies here as well as a key that you'll need to get the second piece of big evidence on the middle deck.
Take the spiral staircase, but watch out for the officer at the top. Move toward the bottom of the screen and pick up the big evidence on the ground near the body, then go right and toss it overboard. Do the same for the body when the cop's patrol route allows it; he moves in a wide enough circle that you can clean up blood while you're waiting for him to move away from the body.
Trying to enter the cabin via the double doors won't work, as they're controlled from a switch behind the bar. Instead, move toward the front of the ship and clean up any blood you find, then enter the orange door to reach the helm. Take the square key from the console, then clean up any remaining blood and dump the body. You'll see a cop spawn on the deck in front of you; be quick, because he'll enter the room from the north side. If you need to hide, go back through the orange door and close it to buy yourself some time.
Go back to the aft deck and north to the port side of the ship; there's a purple door that will let you into the bar. There's still a cop inside, so hide on the stairs immediately to your right if need be. The bar also makes a useful tool for blocking line of sight, and gives you a chance to open the glass doors, but be warned; the circle key can only be picked up from in front of the bar, not behind it.
When the cop goes outside, clean up the blood. You may not have time to wrap the body before he comes back, so be patient and complete the cleanup over multiple cycles if needed. The body can easily be dumped overboard once you get it back out the purple door.
Jacuzzi Area
When you're ready, go up the stairs to reach the pool deck. There are two bodies to clean here, and only a single detective; unfortunately, he tends to stay pretty close to the right-hand body. Try distracting him by making noise with your vacuum from the left, then circling around to deal with the body while he investigates. The body can be dumped near the top of the stairs.
Next, use the circle key you collected from the bar to open the gate on the left and deal with the body there. The detective has a key as well, so he can unlock the gate even if you lock it behind you - try not to attract his attention! If he does come to investigate, hide behind the jet skis until he leaves. When the body is wrapped and ready, it can be thrown overboard from the netting south of its position.
Lower Deck
Once you've cleared the pool deck, go directly down both flights of stairs to return to the middle deck; you'll be in front of the bedroom door, which you can now unlock with the square key. Dump the rifle you find inside, then continue.
Take the stairs to the lowest part of the ship. Immediately south is a corridor covered in blood that also has some evidence. This is a trap. When you're midway down the corridor, a cop will spawn immediately behind you with his nightstick drawn. Run to the end of the hall and open the left-hand door to reach the engine room. Close the door behind you if you can, then go directly left. When the cop enters the room, duck under the low pipes and hide behind machinery to break his line of sight. After a few seconds of searching, he will disappear.
Once the cop despawns, wrap the body in the engine room and dispose of it by tossing it into the machinery in the lower left. If you drag the body instead of carrying it, you can squeeze under the low pipes that you used to evade the cop.
Once the body is dealt with, clean up the corridor and grab the evidence; the cop won't respawn, but another one may appear in the engine room if you linger too long. As soon as the yacht is clean, you can return to the helm to complete the mission!