Neoprene by its nature is waterproof, in an angling situation leaks through the material are rare and easily fixed. However the seams of most are really badly made. The seams are not properly sealed and require internal sealing. This is normally cloth tape, which wears quickly and lifts if not perfectly sealed down.
Aquasure mixed with cotal will seal the seams very easily, mix it 50/50, paint it on over the seams, with a 1cm overlap of the tape and all is well. I did mine 3 times, 25% aquasure to cotal and they have been water tight for years. The seams are now the strongest party of the wader.
Dive shops (AWL) sell the materials, and can do the job. or you can buy the stuff and do it your self.
D