For ease of visualization of Brewster angle, we set up a simple experiment with copper-backed water slab to show near-full transmission of parallel polarization. Using a circularly polarized microstrip patch antenna connected to a portable USB signal generator as the transmitter and a linearly polarized patch with a portable USB spectrum analyzer as the receiver, the low parallel polarization reflection level is observable at the desired angle, calculated with undergraduate-level electromagnetic theory. With the help of the experiment, the effect is intuitively understood and easily reproduced by students in classrooms.