Heat olive oil in a saucepan. Saute onion and ginger in the oil over medium heat until onion is soft (5-7 minutes).
Pour onion mixture over ribs in slow cooker.
Pour teriyaki sauce and water over ribs and onion.
Cover and cook on low for 7-8 hours, or on high for 4 hours. Ribs are done when they are fork-tender and the meat is almost (or actually is) falling off the bone.