The Male Snail can be found in the Sacred Grove. From the Pedestal of Time, travel toward the destroyed staircase. Take a right (Wii) or left (HD) and walk into the cave. Stop a little bit in, and turn around. On the wall Link will see the Male Snail. It can brought down using the Gale Boomerang or the Clawshot.
The Female Snail is also found in the Sacred Grove.