Jump into the water and swim towards Vinnie's ship
First, go to the beach, where Vinnie is waiting for you on the ship. In the sewers, go left and smash the blue-and-white crate to get across the fence and go straight ahead. Over the pillar, jump into the center of the area. There, behind the flames, you will find a valve. Use it. Then, jump to the right, use the rope and then the lever behind the door.
Use the bricks to build a fan, which will lift you. Go right. Destroy the block in the center and build astronaut's box - it will provide you with elements to repair the mechanism. On the left, there is a valve that you need to take. Use the mechanism and mount it behind the grate on the right. Cross the bridge right.
You will have to carry the box outside of the electrified grate - disable the security system first
Destroy the barrel, water the flower pot, climb up and climb across the venting opening on the right. Inside, use color gun swapper and press be button to be able to carry the box outside and place it by the lift.
Here, there are only two actions to perform. First, go left, where there is Blackwell's portrait on the wall above the mantel - pull it down with the rope. This will reveal a scanner. Follow the path and use the bricks that you find to build a terminal.
After that, you will notice a button for which you require the color gun swapper. Do you see the red furniture and a TV on the right? Smash them and you will create one. Then, fire the gun at the button.
Down below, destroy the desk on the right - there is a crate inside. Carry it over and place it by the safe. After you have disabled another button, enter the vault - this will end this chapter.
After the cutscene, you will have to make it over to the indicated square and face a sizeable group of opponents.