Preheat the oil in a deep fryer to 350°F (180°C). Line a baking sheet with paper towels.
In a bowl, combine the water, lemon juice and salt, stirring until the salt has dissolved.
Cook the plantain slices in the oil for 3 minutes or until starting to brown. Drain on the baking sheet and let cool. On a work surface, place a plantain slice and press down with a small plate until flattened to ½ inch (1 cm) thick. Repeat with the remaining slices.
Dip the plantain slices in the salt-water mixture. Drain and immediately return to the fryer. Watch out for splattering. Cook until the plantains are golden and crispy, about 2 to 3 minutes. Drain on the baking sheet. Keep warm until ready to serve.