Place eggplant slices in a large bowl in layers, sprinkling each layer with salt. Let stand for 30 minutes to drain. Rinse and dry on paper towels.

Heat olive oil in a large skillet over medium heat. Whisk together eggs, water, and flour in a medium bowl until batter is smooth. Dip eggplant slices in batter and fry in hot oil until golden brown, working in batches of 2 to 3 slices at a time. Drain on a paper towel-lined plate.

Mix together Parmesan cheese and seasoned bread crumbs in a small bowl until well combined. Place 1/4 of the eggplant slices into a slow cooker and top with 1/4 of the bread crumb mixture, 1/4 of the marinara sauce, and 1/4 of the mozzarella cheese. Repeat layers three more times.

Cover and cook on Low until tender and flavors have blended, 4 to 5 hours.