How do I pick up stuff in the water?

[blkcurtains]

This is probably a stupid question since it's one of the first things the game has you do, and I did it, eventually. My problem is I don't know how I did it. I'm playing the campaign and there are boxes floating in the harbor. I just got the editor's boat, but when I click the boat and click the boxes, the icon changes but I can't pick it up.

[Chaosium]

It's right click but your ship need free cargo slots (equipment slots on the lower part of the command card do not count)