I used a polyurethane woodglue that foams up, and there were voids in between the layers. I didn't use a vacuum, maybe that would help - what do you use to pull the vacuum?
The vacuum pump is important, it gives you a lmainate without any voids and full contact of all the layers. I got my vacuum pump from e-bay, you can also use some airbrush compressors (it if has a threaded intake) or use a 'frige compressor.
The polyurethane glue is impressive stuff, I am not sure how water resistant it is but it seems plenty strong. If you coat the finished board and especially all the end-grain with a good sealer like epoxy it will probably be fine. Then again I am not sure polyurethane glue will cure in a vacuum.
The choice of the wood you use is very important. I use 3 layers 3mm, of a wood that is commonly sold as "baltic birch" which I beleive is imported from Russia. It is a fairly dense and strong wood: way stronger than say, "luan" plywood and even some of the commonly available marine plywoods. If the wood you are using is not as strong, you either have to use more (thicker) layers of wood or consider putting a layer of glass on the bottom and maybe even a layer of glass on the deck as well.