Visual DATA MODEL Designer in linux?

Heu...

I search for a graphical DATA MODEL designer in linux to developp my
database project (to draw) it on screen instead of paper and pencil...

Thanks for answers about Database GUI developper... I will surely need
it later but for now, I want to "draw" boxes etc... on screen for my
tables and interactions.

I don't know about UML (somebody told me about it).

I'd like DBDesigner4 at this moment but I will have to test with ODBC
because it seems that postgresql isn't native support like mysql with
this tool...

Any other suggestions welcome.

I hope this message will be more accurate then the one before :)

Thanks every body for your advices.

Eric.