I have seen this product used in diorama how to books. But cant find it anywhere. Anyone know if it goes by another name or if it can be located on line somewhere? And if anyone has used this as a base is it better than good ole wood? Thanks everyone for your help!
Because of its primary use as a flotation element in boat construction, marine styrofoam is difficult to find in small quantities. My suggestion would be to check marinas, boat fabrication and or repair shops and see if you can hit them up for some scrap or if they’d be willing to part with a sheet ot two. Its usually thick and is cut to the dimensions necessary.
Another source is surfboard fabricators. Guys that do their own shaping use it, and can usually be talked into giving up some scraps or selling small quantities. They may also give you their sources. But again, I’ve rarely found it in small quantities.
If its just a base or for making ground contours, the foam insulation available at any DIY store or even florists foam (the green blocks used for doing floral arrangements) will work fine and carve nicely with rasps, planes, and wire brushes. These are available in 1/2" to 2" sheets and the florist foam is found easily in craft shops. If you want to laminate it together to make thicker pieces, the same stores also sell an adhesive specificaly for foam. When laminating, spred this adhesive out, press the two pieces together and then pull them apart. Let the air hit the adhesive for about 30 seconds and then press the pieces back together. Works great.
Good luck
Mike
Hi Kenny
WELCOME TO THE FORUM!!!
Well when I cant find something I just find a substitute. The best diorama scenes I have made so far were made with the most basic items. Sometimes the pieces you need are staring right at you right now 
Good luck with whatever you choose to use. Post some pics to show us how it is coming along.
thanks for the help guys. i will try your suggestions.