How to get across testchamber 18?

Clue: Look down, near the water

Full answer on how to do the room:

1. Clear turrets if you're a wuss by using the energy balls.

2. Activate the platform by putting the energy ball in the socket. Once you redirect it with the portal, you need to quickly (but not too quickly) portal a couple feet up and hit the button to open the doors protecting the socket.

3. Take the tram across and drop down into the lower alcove

4. Push the button, then quickly portal back to the main platform, placing a portal on the now slanted up, "door" panel. Quickly head to the right and use the platform below near the water to fling yourself out of said portal to where the cube is.

5. Grab cube, drop down to lower alcove (the moving platform can help).

6. Hit button, portal back to the main platform and escape before the panel closes once again

How to do it quickly ("traditional" way of doing a speed run, without jamming doors with cameras or using glitches):

1. Immediately when entering chamber, fling yourself across the room to the cube. Avoid activating turrets as best as possible by hiding behind solid panels (not the glass) while the door opens.

2. Grab cube and drop down to lower alcove

3. Hit button to open panel, portal across and escape.

Deaths to turrets and missing the drop are common. Do your best.

First, you need to activate the platform. To do that, you have to use a portal to redirect the energy ball that is being shot by the turning shooter to the closed, upraised door to your left. Immediately after the energy ball goes through the portal, you need to quickly shoot a portal with one end next to the upraised switch and the other near your feet, then jump through and hit the switch before the energy ball hits the door.

Once that's done, then you need to ride the platform across, jump to the lower platform, hit the switch, put a Portal on the door that just opened (and the other end next to you), go through the Portal, put the non-door end of the portal down the pit to the right of where the screenshot is, and jump through it to long jump using the door portal to reach the top platform on the other side. Then you need to bring the weighted storage cube back over to the near side via the platform, then jump on the platform again to activate the door again...

Phew, that's a lot just to gain one weighted storage cube.