1. Fill a big bowl with water. Using a sharp knife, cut the pomegranate lengthwise through the blossom end into quarters. Holding the quarters under the water, pop the seeds out of the spongy pith and pull off the membranes.
2. The heavier seeds will fall to the bottom, and the lighter membranes and pith will float to the top. Discard the membranes and pith, then drain the water off the seeds.