How long can a red-eared slider survive out of water?

A red-eared slider can survive out of water for at most 7 days; longer causes death by dehydration, faster if left in the sun. So it must not stay out of water too long; even when dry-kept for illness, soak it 3 times a day for about 30 minutes. Also change the water often to keep it clean, since water quality strongly affects its health; avoid both long dry spells and dirty water.