I can't believe this is so hard to find on Google. Someone sent me a documentary video (in Portuguese - unfortunately - but, if you understand German, the creators of this idea speak in their native language) and i can find hardly any references to this online.

It's basically about using a special aluminum powder that, when heated, transforms into a foam that is - check it out - lighter than water. Yes, imagine ships 30% lighter, that can carry many many more tons of materials. Less trips = less pollution = win/win ;)

Here's a link to a 1998 paper about this.

I wonder if this technology is already in use in today's ships and, if not, why?