Maya, Lightwave (that i like the look of) and 3DS..
I would like to create pictures of warships, obviously place them on sea (or space for starships) and fully animate them.
I forgot about Lightwave, it was used for Babylon 5.
3D Studio Max only runs on Windows, but is easy to learn.
Maya had a free (students) version when it was still belonging to Alias, but since it moved to Autodesk, I don't know anymore.
Look at the official webpages to see if those applications might be for you, as the all are capable of doing what you want.
Here is a more comprehensive list of 3D modelling and animation software:
http://www.pure-mac.com/3d.html
via
http://www.google.com/search?client=safari&rls=en&q=3d+software+mac+os+x&ie=UTF-8&oe=UTF-8
But know that getting into 3D might be hard at first, to understand all the modelling (Splines, Nurbs, polygons, ....) techniques.
It took me one year to get a decent animation of some models I made in 3D Studio Max, which was in 1998 or so.
Also have a look at
www.3dcafe.com, it was a great resource of tutorials, models, material (maps, textures) and such, many for free. It might not be this way anymore though.